> So the next problem was that you couldn't query quickly for things that weren't the primary key. So new columns had to be added called "opt_key1" and "opt_key2" where certain rows could put key values, and indexes could be added on those columns, so you could quickly query by it's first optional key, or it's second optional key.

It's all fun and games until you realize DynamoDB works more or less the same way: https://docs.aws.amazon.com/amazondynamodb/latest/developerg...