It should be noted that an EXPIREAT triggers a deletion if the timestamp being set is in the past and could lead to an increase in memory and disk pressure during script execution. Worth checking if the behavior there differs in any meaningful way since y'all made the change. EXPIRE usually just marks a key and relies on either subsequent operations to the same key or garbage collection to actually excise the entry and do the subsequent bookkeeping, I believe.

It's been a while since I had to deal with this kind of problem though, so please tell me if things are different now.