Short answer: give each browser fetch a request ID, carry it to the backend in a standard HTTP header, and emit that same ID in structured logs on both sides. Keep the pricing decision itself behind a flag with an explicit evaluation ID, so a rollback can be verified instead of guessed.
The browser is the first audit surface
Rolling out a new pricing rule in an edtech app sounds like a feature-flag task. Operationally, it is a tracing problem with money attached. A student sees a price in the browser, the frontend calls the checkout backend, and the backend evaluates a flag before writing an order. When those events cannot be joined, a rollback turns into a debate about which request produced which price.
I've been paged for missed jobs and duplicate deliveries. The same failure pattern appears here: a dashboard says the system is healthy, but the individual request that matters is hard to reconstruct. A request ID doesn't prove that a price was correct. It makes the evidence joinable.
The smallest useful contract is straightforward:
