It is hard to replace GCP's managed datastores because I really don't want to maintain my own database server (even if it's a managed service that someone else upgrades for me). So I've stuck to Google Cloud Datastore / Firestore, but I've been experimenting a lot with Litestream[0], and I think that might be my go-to choice in the future instead of proprietary managed datastores.
Litestream continuously streams data from a SQLite database to an S3 backend. It means that you can design your app to use SQLite and then sync the database to any S3 provider. I designed a simple pastebin clone on top of Litestream, and I use it in production for my open source KVM over IP. It's worked great so far, though I'm admittedly putting a pretty gentle workload on it (a handful of requests per day).
Having worked with quite a few ex-Googlers this is a pretty standard Google engineering pattern.
True, I have to maintain state on S3, but there's not much work involved in that.
If I was maintaining my own database server, I have to manage upgrades, backups, and the complexity of running an additional server. With Litestream, I don't have to manage upgrades because nothing bad happens if I don't upgrade, whereas there are security risks running an unpatched MySQL/Postgres server in production. Litestream has built-in snapshots and can replicate to multiple S3 backends, so I'm not too worried about backups. And there's no server to maintain.
What operational complexity do you see in Litestream?
