> How did you work around this problem? As in, how do you monitor for hung queries and cancel them?

You just wrap your DB queries in your own timeout logic. You can then continue your business logic but you can't truly cancel the query because well, the communication layer for it is stuck and you can't kill it via a new connection. Your only choice is to abandon that query. Sometimes we could retry and it would immediately succeed suggesting that the original query probably had something like packetloss that wasn't handled properly by CF. Easy when it's a read but when you have writes then it gets complicated fast and you have to ensure your writes are idempotent. And since they don't support transactions it's even more complex.

Aphyr would have a field day with D1 I'd imagine.

> What about reads? We use D1 in prod & our traffic pattern may not be similar to yours (our workload is async queue-driven & so retries last in order of weeks), nor have we really observed D1 erroring out for extended periods or frequently.

We have reads and writes which most of the time are latency sensitive (direct user feedback). A user interaction can usually involve 3-5 queries and they might need to run in sequence. When queries take 500ms+ the system starts to feel sluggish. When they take 2-3s it's very frustrating. The high latencies happened for both reads and writes, you can do a simple "SELECT 123" and it would hang. You could even reproduce that from the Cloudflare dashboard when it's in this degradated state.

From the comments of others who had similar issues I think it heavily depends on the CF locations or D1 hosts. Most people probably are lucky and don't get one of the faulty D1 servers. But there are a few dozen people who were not so lucky, you can find them complaining on Github, on the CF forum etc. but simply not heard. And you can find these complaints going back years.

This long timeframe without fixes to their network stack (networking is CF's bread and butter!), the refusal to implement transactions, the silence in their forum to cries for help, the absurdly low 10GB limit for databases... it just all adds up. We made the decision to not implement any new product on D1 and just continue using proper databases. It's a shame because workers + a close-by read replica could be absolutely great for latency. Paradoxically it was the opposite outcome.