A nightly VACUUM FULL which ran based on heuristics resolved the problem. This would seem to point to a db problem more than an app problem? I’m unsure how the app could have an affect of this magnitude on the database, although I’d love to be told otherwise.
Not sure what the right answer is but its seems your database (those tables at least) are mis-configured for the workload being executed against them. Significantly increasing the aggressiveness of the auto-vacuum process and/or inserting manual vacuum analyze commands into your application at appropriate times are probably necessary.
