The composition of the average transaction will be different in a shopping cart (lots of writes and updates) compared to your use case which sounds like it skewed read heavy. With Postgres it’s generally easier to scale reads because it doesn’t really matter which replica the query hits, as long as it contains the data it needs. Whereas write-heavy workloads route through a single-writer bottleneck.

There’s challenges scaling read-heavy workloads, for sure — but they’re generally more straight forward than scaling write-heavy workloads. You can get away with more dumb horizontal scaling than with writes.

You don't see how adding functionality that requires writing to the database rather than just reading from a cache could "drastically increase database load"?