Comment by econ

I've never had the luxury of multiple db but in general race conditions..

Could you put an almost empty db in front that only records recent changes? Deletes become rows, updates require posting all values of the row. If no record is found forward the query to the read db. If modifications are posted forward the query to the write db.

If correctness is merely nice to have I always use a "Pain" value that influences the sleep duration. It rarely gets very busy instantaneously, activity usually changes gradually.