All queries run inside transactions, and a slow lane like S3 will cause delays, which will in turn block vacuum and cause more problems than it will solve. Most deployments of Postgres (e.g., RDS) won't let you install custom extensions either, although they do have their own S3 extension (which I wouldn't recommend you use).
The right place to manage this is either in the app or in a proxy, before the data touches Postgres.
All queries run inside transactions, and a slow lane like S3 will cause delays, which will in turn block vacuum and cause more problems than it will solve. Most deployments of Postgres (e.g., RDS) won't let you install custom extensions either, although they do have their own S3 extension (which I wouldn't recommend you use).
The right place to manage this is either in the app or in a proxy, before the data touches Postgres.