That’s what the docs say but if you try to do this you quickly realize that the docs are living in a pipe dream. It’s not possible to set up per-user data in D1. Like in theory you probably could, but the DX infrastructure to make it possible is non-existent - you have to explicitly bind each database into your worker. At best you could try to manually shard data but that has a lot of drawbacks. Or maybe have the worker republish itself whenever a new user is registered? That seems super dangerous and unlikely to work in a concurrent fashion without something like a DO to synchronize everything (you don’t want to publish multiple workers at once with disjoint bindings & you probably want to batch updates to the worker).

When I asked on Discord, someone from Cloudflare confirmed that DO is indeed the only way to do tenancy-based sharding (you give the DO a name to obtain a handle to the specific DO instance to talk to), but the DX experience between DO and D1 is quite stark; D1 has better in DX in many ways but can’t scale, DO can scale but has terrible DX.

> My take from reading some docs is that you've got to partition your data properly, likely per-user.

I dont't think your take makes sense. I'll explain why.

Cloudflare's doc on D1's service limits states that paid plans have a hard limit on 50k databases per paid account. That's roomy for sharding, but you still end up with a database service that is hosted in a single data center whose clients are served from one of the >300 data centers, and whose cache misses still require pulling data from the primary region. Hypothetically sharding does buy you less write contention, but even in read-heavy applications you still end up with all >300 data centers having to pull data from the primary region whenever a single worker does a write.

You may be interested in this new announcement about D1, https://blog.cloudflare.com/d1-read-replication-beta/

Read replicas for lower latency and sessions for partitions per user like you mention.