_Originally posted by @S3RK in https://github.com/bitcoin/bitcoin/pull/24984#pullrequestreview-952900468_

> With current implementation we don't save the rescan progress and on the next load we will have to start from scratch. Is it possible to save the last processed blocked at shutdown?

It would be nice if wallet code would call `WriteBestBlock` and save the last scan position if it is interrupted during a sync. This could be implemented by trying to save the scan position during the shutdown, or by just periodically saving the scan position after an interval, similar to indexing code which saves sync position once every 30 seconds:

https://github.com/bitcoin/bitcoin/blob/f0a834e2f10a0aa60c7cc76e9f3eb090168a32e5/src/index/base.cpp#L170-L175
key.pushKV("scriptPubKey", HexStr(GetScriptForRawPubKey(coinbaseKey.GetPubKey())));
        key.pushKV("timestamp", 0);
        key.pushKV("internal", UniValue(true));
        keys.push_back(key);
        key.clear();
        key.setObject();
        CKey futureKey;
        futureKey.MakeNewKey(true);
        key.pushKV("scriptPubKey", HexStr(GetScriptForRawPubKey(futureKey.GetPubKey())));
        key.pushKV("timestamp", newTip->GetBlockTimeMax() + TIMESTAMP_WINDOW + 1);
        key.pushKV("internal", UniValue(true));
        keys.push_back(key);
        JSONRPCRequest request;
        request.context = &context;
        request.params.setArray();
        request.params.push_back(keys);
        UniValue response = importmulti().HandleRequest(request);
        BOOST_CHECK_EQUAL(response.write(),
            strprintf("[{\"success\":false,\"error\":{\"code\":-1,\"message\":\"Rescan failed for key with creation "
                      "timestamp %d. There was an error reading a block from time %d, which is after or within %d "
                      "seconds of key creation, and could contain transactions pertaining to the key. As a result, "
                      "transactions and coins using this key may not appear in the wallet. This error could be caused "
                      "by pruning or data corruption (see bitcoind log for details) and could be dealt with by "
                      "downloading and rescanning the relevant blocks (see -reindex option and rescanblockchain "
                      "RPC).\"}},{\"success\":true}]",
                              0, oldTip->GetBlockTimeMax(), TIMESTAMP_WINDOW));
        RemoveWallet(context, wallet,  std::nullopt);
    }
}
BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)