But to be fair if you enable both you're paying for 3 servers total instead of 2, you can't read from the HA standby. (I'd imagine there are reasons not to do that anyway, but you don't even have the option of making that compromise to save on the cost)

With RDS Aurora, any of your read replicas can be promoted to read/write master in the event of a failure of your primary master. This happens in 10-15 seconds, and is very fast.

So, you can get the benefit of up to 15 read replicas, and not have to pay for an extra standby server that is sitting idle.

Aha, I probably overlooked read replicas (haven't used RDS in about 1.5 years).

That said, it did take AWS a disturbingly long time to add support for Postgres read replicas.

You're welcome to read frustratingly. I didn't think hard about the word choice.

I suppose disturbingly is meant to imply "It was frustrating to me, and I think it would be frustrating to anyone in the situation of seriously using Postgres on RDS[1], and perhaps it ought to even decrease their opinion of the RDS team's ability to prioritize and ship features that are production-ready".

Does that make sense?

[1]: There was no workaround for getting a read replica. RDS doesn't allow you to run replication commands. So your options were "Don't use Postgres on RDS, or don't run queries against up-to-date copies of databases." There was never any announcement of when read replicas were coming. It was arguably irresponsible of them to release Postgres on RDS as a product and then wait a year to support read replicas, which is a core feature that other DB backends had already.

Without insight into what the AWS RDS team workload and priorities are, I think it's unfair to use a term like disturbingly. Sure, as a user, we want features to be rolled out as quickly as possible. From what I've seen, Postgres RDS support has been slow, but consistently getting better: nothing to warrant suggesting Amazon isn't serious about continuing to improve their Postgres offering. That would be disturbing. Or data loss failures. Slower-than-I'd-like roll-out of new features? Frustrating.

By all means, RDS isn't perfect. It doesn't suit my current needs. But I understand that getting these things to work in a managed way that suits the needs of most customers is not an easy task. I'll remain frustrated in some small way until RDS does suit my needs. I hope they continue to add features to give customers more flexibility. And from what I've seen, they likely will.