diff --git a/src/checkpoints.cpp b/src/checkpoints.cpp
index 9189c9a8ad..816d854db3 100644
--- a/src/checkpoints.cpp
+++ b/src/checkpoints.cpp
@@ -21,9 +21,10 @@ namespace Checkpoints {
         for (const MapCheckpoints::value_type& i : reverse_iterate(checkpoints))
         {
             const uint256& hash = i.second;
-            BlockMap::const_iterator t = mapBlockIndex.find(hash);
-            if (t != mapBlockIndex.end())
-                return t->second;
+            CBlockIndex* pindex = LookupBlockIndex(hash);
+            if (pindex) {
+                return pindex;
+            }
         }
         return nullptr;
     }
diff --git a/src/checkpoints.h b/src/checkpoints.h
index bf935f80a7..564b486393 100644
--- a/src/checkpoints.h
+++ b/src/checkpoints.h
@@ -19,7 +19,7 @@ struct CCheckpointData;
 namespace Checkpoints
 {
 
-//! Returns last CBlockIndex* in mapBlockIndex that is a checkpoint
+//! Returns last CBlockIndex* that is a checkpoint
 CBlockIndex* GetLastCheckpoint(const CCheckpointData& data);
 
 } //namespace Checkpoints
diff --git a/src/init.cpp b/src/init.cpp
index bc23d0ff83..e0efe5c0a2 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1424,6 +1424,8 @@ bool AppInitMain()
 
         uiInterface.InitMessage(_("Loading block index..."));
 
+        LOCK(cs_main);
+
         nStart = GetTimeMillis();
         do {
             try {
@@ -1457,8 +1459,9 @@ bool AppInitMain()
 
                 // If the loaded chain has a wrong genesis, bail out immediately
                 // (we're likely using a testnet datadir, or the other way around).
-                if (!mapBlockIndex.empty() && mapBlockIndex.count(chainparams.GetConsensus().hashGenesisBlock) == 0)
+                if (!mapBlockIndex.empty() && !LookupBlockIndex(chainparams.GetConsensus().hashGenesisBlock)) {
                     return InitError(_("Incorrect or no genesis block found. Wrong datadir for network?"));
+                }
 
                 // Check for changed -txindex state
                 if (fTxIndex != gArgs.GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
@@ -1532,16 +1535,13 @@ bool AppInitMain()
                             MIN_BLOCKS_TO_KEEP);
                     }
 
-                    {
-                        LOCK(cs_main);
-                        CBlockIndex* tip = chainActive.Tip();
-                        RPCNotifyBlockChange(true, tip);
-                        if (tip && tip->nTime > GetAdjustedTime() + 2 * 60 * 60) {
-                            strLoadError = _("The block database contains a block which appears to be from the future. "
-                                    "This may be due to your computer's date and time being set incorrectly. "
-                                    "Only rebuild the block database if you are sure that your computer's date and time are correct");
-                            break;
-                        }
+                    CBlockIndex* tip = chainActive.Tip();
+                    RPCNotifyBlockChange(true, tip);
+                    if (tip && tip->nTime > GetAdjustedTime() + 2 * 60 * 60) {
+                        strLoadError = _("The block database contains a block which appears to be from the future. "
+                                "This may be due to your computer's date and time being set incorrectly. "
+                                "Only rebuild the block database if you are sure that your computer's date and time are correct");
+                        break;
                     }
 
                     if (!CVerifyDB().VerifyDB(chainparams, pcoinsdbview.get(), gArgs.GetArg("-checklevel", DEFAULT_CHECKLEVEL),
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 482a206c8b..f5073fe903 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -374,10 +374,11 @@ void ProcessBlockAvailability(NodeId nodeid) {
     assert(state != nullptr);
 
     if (!state->hashLastUnknownBlock.IsNull()) {
-        BlockMap::iterator itOld = mapBlockIndex.find(state->hashLastUnknownBlock);
-        if (itOld != mapBlockIndex.end() && itOld->second->nChainWork > 0) {
-            if (state->pindexBestKnownBlock == nullptr || itOld->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
-                state->pindexBestKnownBlock = itOld->second;
+        const CBlockIndex* pindex = LookupBlockIndex(state->hashLastUnknownBlock);
+        if (pindex && pindex->nChainWork > 0) {
+            if (state->pindexBestKnownBlock == nullptr || pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
+                state->pindexBestKnownBlock = pindex;
+            }
             state->hashLastUnknownBlock.SetNull();
         }
     }
@@ -390,11 +391,12 @@ void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
 
     ProcessBlockAvailability(nodeid);
 
-    BlockMap::iterator it = mapBlockIndex.find(hash);
-    if (it != mapBlockIndex.end() && it->second->nChainWork > 0) {
+    const CBlockIndex* pindex = LookupBlockIndex(hash);
+    if (pindex && pindex->nChainWork > 0) {
         // An actually better block was announced.
-        if (state->pindexBestKnownBlock == nullptr || it->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
-            state->pindexBestKnownBlock = it->second;
+        if (state->pindexBestKnownBlock == nullptr || pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
+            state->pindexBestKnownBlock = pindex;
+        }
     } else {
         // An unknown block was announced; just assume that the latest one is the best one.
         state->hashLastUnknownBlock = hash;
@@ -1015,7 +1017,7 @@ bool static AlreadyHave(const CInv& inv) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
         }
     case MSG_BLOCK:
     case MSG_WITNESS_BLOCK:
-        return mapBlockIndex.count(inv.hash);
+        return LookupBlockIndex(inv.hash) != nullptr;
     }
     // Don't know what it is, just say we already got one
     return true;
@@ -1082,11 +1084,10 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
     bool need_activate_chain = false;
     {
         LOCK(cs_main);
-        BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
-        if (mi != mapBlockIndex.end())
-        {
-            if (mi->second->nChainTx && !mi->second->IsValid(BLOCK_VALID_SCRIPTS) &&
-                    mi->second->IsValid(BLOCK_VALID_TREE)) {
+        const CBlockIndex* pindex = LookupBlockIndex(inv.hash);
+        if (pindex) {
+            if (pindex->nChainTx && !pindex->IsValid(BLOCK_VALID_SCRIPTS) &&
+                    pindex->IsValid(BLOCK_VALID_TREE)) {
                 // If we have the block and all of its parents, but have not yet validated it,
                 // we might be in the middle of connecting it (ie in the unlock of cs_main
                 // before ActivateBestChain but after AcceptBlock).
@@ -1102,9 +1103,9 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
     }
 
     LOCK(cs_main);
-    BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
-    if (mi != mapBlockIndex.end()) {
-        send = BlockRequestAllowed(mi->second, consensusParams);
+    const CBlockIndex* pindex = LookupBlockIndex(inv.hash);
+    if (pindex) {
+        send = BlockRequestAllowed(pindex, consensusParams);
         if (!send) {
             LogPrint(BCLog::NET, "%s: ignoring request from peer=%i for old block that isn't in the main chain\n", __func__, pfrom->GetId());
         }
@@ -1112,7 +1113,7 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
     const CNetMsgMaker msgMaker(pfrom->GetSendVersion());
     // disconnect node in case we have reached the outbound limit for serving historical blocks
     // never disconnect whitelisted nodes
-    if (send && connman->OutboundTargetReached(true) && ( ((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() > HISTORICAL_BLOCK_AGE)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
+    if (send && connman->OutboundTargetReached(true) && ( ((pindexBestHeader != nullptr) && (pindexBestHeader->GetBlockTime() - pindex->GetBlockTime() > HISTORICAL_BLOCK_AGE)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
     {
         LogPrint(BCLog::NET, "historical block serving limit reached, disconnect peer=%d\n", pfrom->GetId());
 
@@ -1122,7 +1123,7 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
     }
     // Avoid leaking prune-height by never sending blocks below the NODE_NETWORK_LIMITED threshold
     if (send && !pfrom->fWhitelisted && (
-            (((pfrom->GetLocalServices() & NODE_NETWORK_LIMITED) == NODE_NETWORK_LIMITED) && ((pfrom->GetLocalServices() & NODE_NETWORK) != NODE_NETWORK) && (chainActive.Tip()->nHeight - mi->second->nHeight > (int)NODE_NETWORK_LIMITED_MIN_BLOCKS + 2 /* add two blocks buffer extension for possible races */) )
+            (((pfrom->GetLocalServices() & NODE_NETWORK_LIMITED) == NODE_NETWORK_LIMITED) && ((pfrom->GetLocalServices() & NODE_NETWORK) != NODE_NETWORK) && (chainActive.Tip()->nHeight - pindex->nHeight > (int)NODE_NETWORK_LIMITED_MIN_BLOCKS + 2 /* add two blocks buffer extension for possible races */) )
        )) {
         LogPrint(BCLog::NET, "Ignore block request below NODE_NETWORK_LIMITED threshold from peer=%d\n", pfrom->GetId());
 
@@ -1132,15 +1133,15 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
     }
     // Pruned nodes may have deleted the block, so check whether
     // it's available before trying to send.
-    if (send && (mi->second->nStatus & BLOCK_HAVE_DATA))
+    if (send && (pindex->nStatus & BLOCK_HAVE_DATA))
     {
         std::shared_ptr<const CBlock> pblock;
-        if (a_recent_block && a_recent_block->GetHash() == (*mi).second->GetBlockHash()) {
+        if (a_recent_block && a_recent_block->GetHash() == pindex->GetBlockHash()) {
             pblock = a_recent_block;
         } else {
             // Send block from disk
             std::shared_ptr<CBlock> pblockRead = std::make_shared<CBlock>();
-            if (!ReadBlockFromDisk(*pblockRead, (*mi).second, consensusParams))
+            if (!ReadBlockFromDisk(*pblockRead, pindex, consensusParams))
                 assert(!"cannot load block from disk");
             pblock = pblockRead;
         }
@@ -1182,8 +1183,8 @@ void static ProcessGetBlockData(CNode* pfrom, const Consensus::Params& consensus
             // instead we respond with the full, non-compact block.
             bool fPeerWantsWitness = State(pfrom->GetId())->fWantsCmpctWitness;
             int nSendFlags = fPeerWantsWitness ? 0 : SERIALIZE_TRANSACTION_NO_WITNESS;
-            if (CanDirectFetch(consensusParams) && mi->second->nHeight >= chainActive.Height() - MAX_CMPCTBLOCK_DEPTH) {
-                if ((fPeerWantsWitness || !fWitnessesPresentInARecentCompactBlock) && a_recent_compact_block && a_recent_compact_block->header.GetHash() == mi->second->GetBlockHash()) {
+            if (CanDirectFetch(consensusParams) && pindex->nHeight >= chainActive.Height() - MAX_CMPCTBLOCK_DEPTH) {
+                if ((fPeerWantsWitness || !fWitnessesPresentInARecentCompactBlock) && a_recent_compact_block && a_recent_compact_block->header.GetHash() == pindex->GetBlockHash()) {
                     connman->PushMessage(pfrom, msgMaker.Make(nSendFlags, NetMsgType::CMPCTBLOCK, *a_recent_compact_block));
                 } else {
                     CBlockHeaderAndShortTxIDs cmpctblock(*pblock, fPeerWantsWitness);
@@ -1323,7 +1324,7 @@ bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::ve
         //   don't connect before giving DoS points
         // - Once a headers message is received that is valid and does connect,
         //   nUnconnectingHeaders gets reset back to 0.
-        if (mapBlockIndex.find(headers[0].hashPrevBlock) == mapBlockIndex.end() && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
+        if (!LookupBlockIndex(headers[0].hashPrevBlock) && nCount < MAX_BLOCKS_TO_ANNOUNCE) {
             nodestate->nUnconnectingHeaders++;
             connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
             LogPrint(BCLog::NET, "received header %s: missing prev block %s, sending getheaders (%d) to end (peer=%d, nUnconnectingHeaders=%d)\n",
@@ -1353,7 +1354,7 @@ bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::ve
 
         // If we don't have the last header, then they'll have given us
         // something new (if these headers are valid).
-        if (mapBlockIndex.find(hashLastBlock) == mapBlockIndex.end()) {
+        if (!LookupBlockIndex(hashLastBlock)) {
             received_new_header = true;
         }
     }
@@ -1369,7 +1370,7 @@ bool static ProcessHeadersMessage(CNode *pfrom, CConnman *connman, const std::ve
             } else {
                 LogPrint(BCLog::NET, "peer=%d: invalid header received\n", pfrom->GetId());
             }
-            if (punish_duplicate_invalid && mapBlockIndex.find(first_invalid_header.GetHash()) != mapBlockIndex.end()) {
+            if (punish_duplicate_invalid && LookupBlockIndex(first_invalid_header.GetHash())) {
                 // Goal: don't allow outbound peers to use up our outbound
                 // connection slots if they are on incompatible chains.
                 //
@@ -2050,13 +2051,13 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
 
         LOCK(cs_main);
 
-        BlockMap::iterator it = mapBlockIndex.find(req.blockhash);
-        if (it == mapBlockIndex.end() || !(it->second->nStatus & BLOCK_HAVE_DATA)) {
+        const CBlockIndex* pindex = LookupBlockIndex(req.blockhash);
+        if (!pindex || !(pindex->nStatus & BLOCK_HAVE_DATA)) {
             LogPrint(BCLog::NET, "Peer %d sent us a getblocktxn for a block we don't have", pfrom->GetId());
             return true;
         }
 
-        if (it->second->nHeight < chainActive.Height() - MAX_BLOCKTXN_DEPTH) {
+        if (pindex->nHeight < chainActive.Height() - MAX_BLOCKTXN_DEPTH) {
             // If an older block is requested (should never happen in practice,
             // but can happen in tests) send a block response instead of a
             // blocktxn response. Sending a full block response instead of a
@@ -2074,7 +2075,7 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         }
 
         CBlock block;
-        bool ret = ReadBlockFromDisk(block, it->second, chainparams.GetConsensus());
+        bool ret = ReadBlockFromDisk(block, pindex, chainparams.GetConsensus());
         assert(ret);
 
         SendBlockTransactions(block, req, pfrom, connman);
@@ -2098,10 +2099,10 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         if (locator.IsNull())
         {
             // If locator is null, return the hashStop block
-            BlockMap::iterator mi = mapBlockIndex.find(hashStop);
-            if (mi == mapBlockIndex.end())
+            pindex = LookupBlockIndex(hashStop);
+            if (!pindex) {
                 return true;
-            pindex = (*mi).second;
+            }
 
             if (!BlockRequestAllowed(pindex, chainparams.GetConsensus())) {
                 LogPrint(BCLog::NET, "%s: ignoring request from peer=%i for old block header that isn't in the main chain\n", __func__, pfrom->GetId());
@@ -2340,14 +2341,14 @@ bool static ProcessMessage(CNode* pfrom, const std::string& strCommand, CDataStr
         {
         LOCK(cs_main);
 
-        if (mapBlockIndex.find(cmpctblock.header.hashPrevBlock) == mapBlockIndex.end()) {
+        if (!LookupBlockIndex(cmpctblock.header.hashPrevBlock)) {
             // Doesn't connect (or is genesis), instead of DoSing in AcceptBlockHeader, request deeper headers
             if (!IsInitialBlockDownload())
                 connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), uint256()));
             return true;
         }
 
-        if (mapBlockIndex.find(cmpctblock.header.GetHash()) == mapBlockIndex.end()) {
+        if (!LookupBlockIndex(cmpctblock.header.GetHash())) {
             received_new_header = true;
         }
         }
@@ -3329,9 +3330,8 @@ bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptM
                 // then send all headers past that one.  If we come across any
                 // headers that aren't on chainActive, give up.
                 for (const uint256 &hash : pto->vBlockHashesToAnnounce) {
-                    BlockMap::iterator mi = mapBlockIndex.find(hash);
-                    assert(mi != mapBlockIndex.end());
-                    const CBlockIndex *pindex = mi->second;
+                    const CBlockIndex* pindex = LookupBlockIndex(hash);
+                    assert(pindex);
                     if (chainActive[pindex->nHeight] != pindex) {
                         // Bail out if we reorged away from this block
                         fRevertToInv = true;
@@ -3422,9 +3422,8 @@ bool PeerLogicValidation::SendMessages(CNode* pto, std::atomic<bool>& interruptM
                 // in the past.
                 if (!pto->vBlockHashesToAnnounce.empty()) {
                     const uint256 &hashToAnnounce = pto->vBlockHashesToAnnounce.back();
-                    BlockMap::iterator mi = mapBlockIndex.find(hashToAnnounce);
-                    assert(mi != mapBlockIndex.end());
-                    const CBlockIndex *pindex = mi->second;
+                    const CBlockIndex* pindex = LookupBlockIndex(hashToAnnounce);
+                    assert(pindex);
 
                     // Warn if we're announcing a block that is not on the main chain.
                     // This should be very rare and could be optimized out.
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index 19cdb0fdea..cc30cf747d 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -167,10 +167,7 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
     // Determine transaction status
 
     // Find the block the tx is in
-    CBlockIndex* pindex = nullptr;
-    BlockMap::iterator mi = mapBlockIndex.find(wtx.hashBlock);
-    if (mi != mapBlockIndex.end())
-        pindex = (*mi).second;
+    const CBlockIndex* pindex = LookupBlockIndex(wtx.hashBlock);
 
     // Sort order, unrecorded transactions sort to the top
     status.sortKey = strprintf("%010d-%01d-%010u-%03d",
diff --git a/src/rest.cpp b/src/rest.cpp
index 8cba59dbbc..f47b40343b 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -147,8 +147,7 @@ static bool rest_headers(HTTPRequest* req,
     headers.reserve(count);
     {
         LOCK(cs_main);
-        BlockMap::const_iterator it = mapBlockIndex.find(hash);
-        const CBlockIndex *pindex = (it != mapBlockIndex.end()) ? it->second : nullptr;
+        const CBlockIndex* pindex = LookupBlockIndex(hash);
         while (pindex != nullptr && chainActive.Contains(pindex)) {
             headers.push_back(pindex);
             if (headers.size() == (unsigned long)count)
@@ -212,10 +211,11 @@ static bool rest_block(HTTPRequest* req,
     CBlockIndex* pblockindex = nullptr;
     {
         LOCK(cs_main);
-        if (mapBlockIndex.count(hash) == 0)
+        pblockindex = LookupBlockIndex(hash);
+        if (!pblockindex) {
             return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
+        }
 
-        pblockindex = mapBlockIndex[hash];
         if (fHavePruned && !(pblockindex->nStatus & BLOCK_HAVE_DATA) && pblockindex->nTx > 0)
             return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not available (pruned data)");
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index f2a1fd048f..2077723af5 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -709,10 +709,10 @@ UniValue getblockheader(const JSONRPCRequest& request)
     if (!request.params[1].isNull())
         fVerbose = request.params[1].get_bool();
 
-    if (mapBlockIndex.count(hash) == 0)
+    const CBlockIndex* pblockindex = LookupBlockIndex(hash);
+    if (!pblockindex) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
-
-    CBlockIndex* pblockindex = mapBlockIndex[hash];
+    }
 
     if (!fVerbose)
     {
@@ -788,12 +788,12 @@ UniValue getblock(const JSONRPCRequest& request)
             verbosity = request.params[1].get_bool() ? 1 : 0;
     }
 
-    if (mapBlockIndex.count(hash) == 0)
+    const CBlockIndex* pblockindex = LookupBlockIndex(hash);
+    if (!pblockindex) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+    }
 
     CBlock block;
-    CBlockIndex* pblockindex = mapBlockIndex[hash];
-
     if (fHavePruned && !(pblockindex->nStatus & BLOCK_HAVE_DATA) && pblockindex->nTx > 0)
         throw JSONRPCError(RPC_MISC_ERROR, "Block not available (pruned data)");
 
@@ -858,7 +858,7 @@ static bool GetUTXOStats(CCoinsView *view, CCoinsStats &stats)
     stats.hashBlock = pcursor->GetBestBlock();
     {
         LOCK(cs_main);
-        stats.nHeight = mapBlockIndex.find(stats.hashBlock)->second->nHeight;
+        stats.nHeight = LookupBlockIndex(stats.hashBlock)->nHeight;
     }
     ss << stats.hashBlock;
     uint256 prevkey;
@@ -1041,8 +1041,7 @@ UniValue gettxout(const JSONRPCRequest& request)
         }
     }
 
-    BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
-    CBlockIndex *pindex = it->second;
+    const CBlockIndex* pindex = LookupBlockIndex(pcoinsTip->GetBestBlock());
     ret.pushKV("bestblock", pindex->GetBlockHash().GetHex());
     if (coin.nHeight == MEMPOOL_HEIGHT) {
         ret.pushKV("confirmations", 0);
@@ -1436,10 +1435,10 @@ UniValue preciousblock(const JSONRPCRequest& request)
 
     {
         LOCK(cs_main);
-        if (mapBlockIndex.count(hash) == 0)
+        pblockindex = LookupBlockIndex(hash);
+        if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
-
-        pblockindex = mapBlockIndex[hash];
+        }
     }
 
     CValidationState state;
@@ -1472,10 +1471,11 @@ UniValue invalidateblock(const JSONRPCRequest& request)
 
     {
         LOCK(cs_main);
-        if (mapBlockIndex.count(hash) == 0)
+        CBlockIndex* pblockindex = LookupBlockIndex(hash);
+        if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+        }
 
-        CBlockIndex* pblockindex = mapBlockIndex[hash];
         InvalidateBlock(state, Params(), pblockindex);
     }
 
@@ -1510,10 +1510,11 @@ UniValue reconsiderblock(const JSONRPCRequest& request)
 
     {
         LOCK(cs_main);
-        if (mapBlockIndex.count(hash) == 0)
+        CBlockIndex* pblockindex = LookupBlockIndex(hash);
+        if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
+        }
 
-        CBlockIndex* pblockindex = mapBlockIndex[hash];
         ResetBlockFailureFlags(pblockindex);
     }
 
@@ -1560,11 +1561,10 @@ UniValue getchaintxstats(const JSONRPCRequest& request)
     } else {
         uint256 hash = uint256S(request.params[1].get_str());
         LOCK(cs_main);
-        auto it = mapBlockIndex.find(hash);
-        if (it == mapBlockIndex.end()) {
+        pindex = LookupBlockIndex(hash);
+        if (!pindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
-        pindex = it->second;
         if (!chainActive.Contains(pindex)) {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Block is not in main chain");
         }
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index 3073a49d0d..0537628763 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -396,9 +396,8 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
                 throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "Block decode failed");
 
             uint256 hash = block.GetHash();
-            BlockMap::iterator mi = mapBlockIndex.find(hash);
-            if (mi != mapBlockIndex.end()) {
-                CBlockIndex *pindex = mi->second;
+            const CBlockIndex* pindex = LookupBlockIndex(hash);
+            if (pindex) {
                 if (pindex->IsValid(BLOCK_VALID_SCRIPTS))
                     return "duplicate";
                 if (pindex->nStatus & BLOCK_FAILED_MASK)
@@ -727,9 +726,8 @@ UniValue submitblock(const JSONRPCRequest& request)
     bool fBlockPresent = false;
     {
         LOCK(cs_main);
-        BlockMap::iterator mi = mapBlockIndex.find(hash);
-        if (mi != mapBlockIndex.end()) {
-            CBlockIndex *pindex = mi->second;
+        const CBlockIndex* pindex = LookupBlockIndex(hash);
+        if (pindex) {
             if (pindex->IsValid(BLOCK_VALID_SCRIPTS)) {
                 return "duplicate";
             }
@@ -743,9 +741,9 @@ UniValue submitblock(const JSONRPCRequest& request)
 
     {
         LOCK(cs_main);
-        BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
-        if (mi != mapBlockIndex.end()) {
-            UpdateUncommittedBlockStructures(block, mi->second, Params().GetConsensus());
+        const CBlockIndex* pindex = LookupBlockIndex(block.hashPrevBlock);
+        if (pindex) {
+            UpdateUncommittedBlockStructures(block, pindex, Params().GetConsensus());
         }
     }
 
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 883ec71747..20bfd3f355 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -48,9 +48,8 @@ void TxToJSON(const CTransaction& tx, const uint256 hashBlock, UniValue& entry)
 
     if (!hashBlock.IsNull()) {
         entry.pushKV("blockhash", hashBlock.GetHex());
-        BlockMap::iterator mi = mapBlockIndex.find(hashBlock);
-        if (mi != mapBlockIndex.end() && (*mi).second) {
-            CBlockIndex* pindex = (*mi).second;
+        CBlockIndex* pindex = LookupBlockIndex(hashBlock);
+        if (pindex) {
             if (chainActive.Contains(pindex)) {
                 entry.pushKV("confirmations", 1 + chainActive.Height() - pindex->nHeight);
                 entry.pushKV("time", pindex->GetBlockTime());
@@ -160,11 +159,10 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
 
     if (!request.params[2].isNull()) {
         uint256 blockhash = ParseHashV(request.params[2], "parameter 3");
-        BlockMap::iterator it = mapBlockIndex.find(blockhash);
-        if (it == mapBlockIndex.end()) {
+        blockindex = LookupBlockIndex(blockhash);
+        if (!blockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block hash not found");
         }
-        blockindex = it->second;
         in_active_chain = chainActive.Contains(blockindex);
     }
 
@@ -238,9 +236,10 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
     if (!request.params[1].isNull())
     {
         hashBlock = uint256S(request.params[1].get_str());
-        if (!mapBlockIndex.count(hashBlock))
+        pblockindex = LookupBlockIndex(hashBlock);
+        if (!pblockindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
-        pblockindex = mapBlockIndex[hashBlock];
+        }
     } else {
         // Loop through txids and try to find which block they're in. Exit loop once a block is found.
         for (const auto& tx : setTxids) {
@@ -257,9 +256,10 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
         CTransactionRef tx;
         if (!GetTransaction(oneTxid, tx, Params().GetConsensus(), hashBlock, false) || hashBlock.IsNull())
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction not yet in block");
-        if (!mapBlockIndex.count(hashBlock))
+        pblockindex = LookupBlockIndex(hashBlock);
+        if (!pblockindex) {
             throw JSONRPCError(RPC_INTERNAL_ERROR, "Transaction index corrupt");
-        pblockindex = mapBlockIndex[hashBlock];
+        }
     }
 
     CBlock block;
@@ -306,8 +306,10 @@ UniValue verifytxoutproof(const JSONRPCRequest& request)
 
     LOCK(cs_main);
 
-    if (!mapBlockIndex.count(merkleBlock.header.GetHash()) || !chainActive.Contains(mapBlockIndex[merkleBlock.header.GetHash()]))
+    const CBlockIndex* pindex = LookupBlockIndex(merkleBlock.header.GetHash());
+    if (!pindex || !chainActive.Contains(pindex)) {
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
+    }
 
     for (const uint256& hash : vMatch)
         res.push_back(hash.GetHex());
diff --git a/src/validation.cpp b/src/validation.cpp
index c677f44b3e..f49dc5a155 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -260,12 +260,12 @@ namespace {
 
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
 {
+    AssertLockHeld(cs_main);
+
     // Find the first block the caller has in the main chain
     for (const uint256& hash : locator.vHave) {
-        BlockMap::iterator mi = mapBlockIndex.find(hash);
-        if (mi != mapBlockIndex.end())
-        {
-            CBlockIndex* pindex = (*mi).second;
+        CBlockIndex* pindex = LookupBlockIndex(hash);
+        if (pindex) {
             if (chain.Contains(pindex))
                 return pindex;
             if (pindex->GetAncestor(chain.Height()) == chain.Tip()) {
@@ -1316,7 +1316,7 @@ bool CScriptCheck::operator()() {
 int GetSpendHeight(const CCoinsViewCache& inputs)
 {
     LOCK(cs_main);
-    CBlockIndex* pindexPrev = mapBlockIndex.find(inputs.GetBestBlock())->second;
+    CBlockIndex* pindexPrev = LookupBlockIndex(inputs.GetBestBlock());
     return pindexPrev->nHeight + 1;
 }
 
@@ -2826,6 +2826,8 @@ bool ResetBlockFailureFlags(CBlockIndex *pindex) {
 
 CBlockIndex* CChainState::AddToBlockIndex(const CBlockHeader& block)
 {
+    AssertLockHeld(cs_main);
+
     // Check for duplicate
     uint256 hash = block.GetHash();
     BlockMap::iterator it = mapBlockIndex.find(hash);
@@ -3272,7 +3274,6 @@ bool CChainState::AcceptBlockHeader(const CBlockHeader& block, CValidationState&
     BlockMap::iterator miSelf = mapBlockIndex.find(hash);
     CBlockIndex *pindex = nullptr;
     if (hash != chainparams.GetConsensus().hashGenesisBlock) {
-
         if (miSelf != mapBlockIndex.end()) {
             // Block header is already known.
             pindex = miSelf->second;
@@ -3706,6 +3707,8 @@ fs::path GetBlockPosFilename(const CDiskBlockPos &pos, const char *prefix)
 
 CBlockIndex * CChainState::InsertBlockIndex(const uint256& hash)
 {
+    AssertLockHeld(cs_main);
+
     if (hash.IsNull())
         return nullptr;
 
@@ -3833,6 +3836,8 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
 
 bool LoadChainTip(const CChainParams& chainparams)
 {
+    AssertLockHeld(cs_main);
+
     if (chainActive.Tip() && chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) return true;
 
     if (pcoinsTip->GetBestBlock().IsNull() && mapBlockIndex.size() == 1) {
@@ -3846,10 +3851,11 @@ bool LoadChainTip(const CChainParams& chainparams)
     }
 
     // Load pointer to end of best chain
-    BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
-    if (it == mapBlockIndex.end())
+    CBlockIndex* pindex = LookupBlockIndex(pcoinsTip->GetBestBlock());
+    if (!pindex) {
         return false;
-    chainActive.SetTip(it->second);
+    }
+    chainActive.SetTip(pindex);
 
     g_chainstate.PruneBlockIndexCandidates();
 
@@ -4296,26 +4302,31 @@ bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskB
                 blkdat >> block;
                 nRewind = blkdat.GetPos();
 
-                // detect out of order blocks, and store them for later
                 uint256 hash = block.GetHash();
-                if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex.find(block.hashPrevBlock) == mapBlockIndex.end()) {
-                    LogPrint(BCLog::REINDEX, "%s: Out of order block %s, parent %s not known\n", __func__, hash.ToString(),
-                            block.hashPrevBlock.ToString());
-                    if (dbp)
-                        mapBlocksUnknownParent.insert(std::make_pair(block.hashPrevBlock, *dbp));
-                    continue;
-                }
-
-                // process in case the block isn't known yet
-                if (mapBlockIndex.count(hash) == 0 || (mapBlockIndex[hash]->nStatus & BLOCK_HAVE_DATA) == 0) {
+                {
                     LOCK(cs_main);
-                    CValidationState state;
-                    if (g_chainstate.AcceptBlock(pblock, state, chainparams, nullptr, true, dbp, nullptr))
-                        nLoaded++;
-                    if (state.IsError())
-                        break;
-                } else if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex[hash]->nHeight % 1000 == 0) {
-                    LogPrint(BCLog::REINDEX, "Block Import: already had block %s at height %d\n", hash.ToString(), mapBlockIndex[hash]->nHeight);
+                    // detect out of order blocks, and store them for later
+                    if (hash != chainparams.GetConsensus().hashGenesisBlock && !LookupBlockIndex(block.hashPrevBlock)) {
+                        LogPrint(BCLog::REINDEX, "%s: Out of order block %s, parent %s not known\n", __func__, hash.ToString(),
+                                block.hashPrevBlock.ToString());
+                        if (dbp)
+                            mapBlocksUnknownParent.insert(std::make_pair(block.hashPrevBlock, *dbp));
+                        continue;
+                    }
+
+                    // process in case the block isn't known yet
+                    CBlockIndex* pindex = LookupBlockIndex(hash);
+                    if (!pindex || (pindex->nStatus & BLOCK_HAVE_DATA) == 0) {
+                      CValidationState state;
+                      if (g_chainstate.AcceptBlock(pblock, state, chainparams, nullptr, true, dbp, nullptr)) {
+                          nLoaded++;
+                      }
+                      if (state.IsError()) {
+                          break;
+                      }
+                    } else if (hash != chainparams.GetConsensus().hashGenesisBlock && pindex->nHeight % 1000 == 0) {
+                      LogPrint(BCLog::REINDEX, "Block Import: already had block %s at height %d\n", hash.ToString(), pindex->nHeight);
+                    }
                 }
 
                 // Activate the genesis block so normal node progress can continue
diff --git a/src/validation.h b/src/validation.h
index 99cbfdf1ee..e780f453b2 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -428,6 +428,13 @@ public:
 /** Replay blocks that aren't fully applied to the database. */
 bool ReplayBlocks(const CChainParams& params, CCoinsView* view);
 
+inline CBlockIndex* LookupBlockIndex(const uint256& hash)
+{
+    AssertLockHeld(cs_main);
+    BlockMap::const_iterator it = mapBlockIndex.find(hash);
+    return it == mapBlockIndex.end() ? nullptr : it->second;
+}
+
 /** Find the last common block between the parameter chain and a locator. */
 CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator);
 
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index c7c54ecb9b..01125dd618 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -350,9 +350,10 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
     if (merkleBlock.txn.ExtractMatches(vMatch, vIndex) == merkleBlock.header.hashMerkleRoot) {
 
         LOCK(cs_main);
-
-        if (!mapBlockIndex.count(merkleBlock.header.GetHash()) || !chainActive.Contains(mapBlockIndex[merkleBlock.header.GetHash()]))
+        const CBlockIndex* pindex = LookupBlockIndex(merkleBlock.header.GetHash());
+        if (!pindex || !chainActive.Contains(pindex)) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found in chain");
+        }
 
         std::vector<uint256>::const_iterator it;
         if ((it = std::find(vMatch.begin(), vMatch.end(), hashTx))==vMatch.end()) {
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 457abec1bc..c02c1bd18d 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -95,7 +95,7 @@ void WalletTxToJSON(const CWalletTx& wtx, UniValue& entry)
     {
         entry.pushKV("blockhash", wtx.hashBlock.GetHex());
         entry.pushKV("blockindex", wtx.nIndex);
-        entry.pushKV("blocktime", mapBlockIndex[wtx.hashBlock]->GetBlockTime());
+        entry.pushKV("blocktime", LookupBlockIndex(wtx.hashBlock)->GetBlockTime());
     } else {
         entry.pushKV("trusted", wtx.IsTrusted());
     }
@@ -2043,11 +2043,10 @@ UniValue listsinceblock(const JSONRPCRequest& request)
         uint256 blockId;
 
         blockId.SetHex(request.params[0].get_str());
-        BlockMap::iterator it = mapBlockIndex.find(blockId);
-        if (it == mapBlockIndex.end()) {
+        paltindex = pindex = LookupBlockIndex(blockId);
+        if (!pindex) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Block not found");
         }
-        paltindex = pindex = it->second;
         if (chainActive[pindex->nHeight] != pindex) {
             // the block being asked for is a part of a deactivated chain;
             // we don't want to depend on its perceived height in the block
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 0c468878e1..e1f940e114 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1147,11 +1147,9 @@ void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
     LOCK2(cs_main, cs_wallet);
 
     int conflictconfirms = 0;
-    if (mapBlockIndex.count(hashBlock)) {
-        CBlockIndex* pindex = mapBlockIndex[hashBlock];
-        if (chainActive.Contains(pindex)) {
-            conflictconfirms = -(chainActive.Height() - pindex->nHeight + 1);
-        }
+    CBlockIndex* pindex = LookupBlockIndex(hashBlock);
+    if (pindex && chainActive.Contains(pindex)) {
+        conflictconfirms = -(chainActive.Height() - pindex->nHeight + 1);
     }
     // If number of conflict confirms cannot be determined, this means
     // that the block is still unknown or not yet part of the main chain,
@@ -3767,10 +3765,10 @@ void CWallet::GetKeyBirthTimes(std::map<CTxDestination, int64_t> &mapKeyBirth) c
     for (const auto& entry : mapWallet) {
         // iterate over all wallet transactions...
         const CWalletTx &wtx = entry.second;
-        BlockMap::const_iterator blit = mapBlockIndex.find(wtx.hashBlock);
-        if (blit != mapBlockIndex.end() && chainActive.Contains(blit->second)) {
+        CBlockIndex* pindex = LookupBlockIndex(wtx.hashBlock);
+        if (pindex && chainActive.Contains(pindex)) {
             // ... which are already in a block
-            int nHeight = blit->second->nHeight;
+            int nHeight = pindex->nHeight;
             for (const CTxOut &txout : wtx.tx->vout) {
                 // iterate over all their outputs
                 CAffectedKeysVisitor(*this, vAffected).Process(txout.scriptPubKey);
@@ -3778,7 +3776,7 @@ void CWallet::GetKeyBirthTimes(std::map<CTxDestination, int64_t> &mapKeyBirth) c
                     // ... and all their affected keys
                     std::map<CKeyID, CBlockIndex*>::iterator rit = mapKeyFirstBlock.find(keyid);
                     if (rit != mapKeyFirstBlock.end() && nHeight < rit->second->nHeight)
-                        rit->second = blit->second;
+                        rit->second = pindex;
                 }
                 vAffected.clear();
             }
@@ -3815,7 +3813,12 @@ unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
 {
     unsigned int nTimeSmart = wtx.nTimeReceived;
     if (!wtx.hashUnset()) {
-        if (mapBlockIndex.count(wtx.hashBlock)) {
+        const CBlockIndex* pindex = nullptr;
+        {
+            LOCK(cs_main);
+            pindex = LookupBlockIndex(wtx.hashBlock);
+        }
+        if (pindex) {
             int64_t latestNow = wtx.nTimeReceived;
             int64_t latestEntry = 0;
 
@@ -3846,7 +3849,7 @@ unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx) const
                 }
             }
 
-            int64_t blocktime = mapBlockIndex[wtx.hashBlock]->GetBlockTime();
+            int64_t blocktime = pindex->GetBlockTime();
             nTimeSmart = std::max(latestEntry, std::min(blocktime, latestNow));
         } else {
             LogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.hashBlock.ToString());
@@ -4016,6 +4019,8 @@ CWallet* CWallet::CreateWalletFromFile(const std::string& name, const fs::path&
     // Try to top up keypool. No-op if the wallet is locked.
     walletInstance->TopUpKeyPool();
 
+    LOCK(cs_main);
+
     CBlockIndex *pindexRescan = chainActive.Genesis();
     if (!gArgs.GetBoolArg("-rescan", false))
     {
@@ -4159,10 +4164,7 @@ int CMerkleTx::GetDepthInMainChain(const CBlockIndex* &pindexRet) const
     AssertLockHeld(cs_main);
 
     // Find the block it claims to be in
-    BlockMap::iterator mi = mapBlockIndex.find(hashBlock);
-    if (mi == mapBlockIndex.end())
-        return 0;
-    CBlockIndex* pindex = (*mi).second;
+    CBlockIndex* pindex = LookupBlockIndex(hashBlock);
     if (!pindex || !chainActive.Contains(pindex))
         return 0;