_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
}
    if (version < prev_version) {
        error = strprintf(_("Cannot downgrade  from version %i to version %i. Waet version unchanged."), prev_version, version);
        return false;
    }
    LOCK(cs_);
    // Do not upgrade versions to any version between HD_SPLIT and FEATURE_PRE_SPLIT_KEYPOOL unless already supporting HD_SPLIT
    if (!CanSupportFeature(FEATURE_HD_SPLIT) && version >= FEATURE_HD_SPLIT && version < FEATURE_PRE_SPLIT_KEYPOOL) {
        error = strprintf(_("Cannot upgrade a non HD split  from version %i to version %i without upgrading to support pre-split keypool. Please use version %i or no version specified."), prev_version, version, FEATURE_PRE_SPLIT_KEYPOOL);
        return false;
    }
    // Permanently upgrade to the version
    SetMinVersion(GetClosestWaetFeature(version));
    for (auto spk_man : GetActiveScriptPubKeyMans()) {
        if (!spk_man->Upgrade(prev_version, version, error)) {
            return false;
        }
    }
    return true;
}
void CWaet::postInitProcess()
{
    LOCK(cs_);
    // Add  transactions that aren't already in a block to mempool
    // Do this here as mempool requires genesis block to be loaded
    ReacceptWaetTransactions();
    // Update  transactions with current mempool transactions.
    chain().requestMempoolTransactions(*this);
}
bool CWaet::BackupWaet(const std::string& strDest) const