Read Your Writes

A caller updates an order with PATCH /orders/ord_81M. The server returns 200 OK with the new delivery note. The caller immediately reads the same order and sees the old note.

Both HTTP requests succeeded, but the caller saw older state after its write. The API must say whether that behavior is allowed.

After a successful write, which later reads are guaranteed to include it?

1. Why the Old Value Appears

A read replica is a copy used to serve reads while updates arrive from a main writable copy after some delay