The short answer
Translate the PRD into an end-to-end user journey and observable acceptance checks. Build the interface and real backend together, test failure paths, deploy to an agreed environment and pilot with the intended users. Keep a clear list of unfinished requirements and the next release.
Start with a transaction, not a feature list
“A booking app with AI” is too broad to estimate. “A customer can choose a valid slot, reserve it and receive a confirmation” is testable. Add the staff side: someone can edit availability, see the reservation and handle a cancellation. This reveals the minimum product more reliably than a long list of screens.
Write the rules before the happy-path demo
Specify who can see each record, which system owns it, how duplicates are handled and what happens when an integration is down. For every external call, decide whether it can be retried and how the user sees a pending action. A slow payment confirmation should produce a pending state, not a second charge attempt.
Choose what must be real
Use real persistence and business logic for the core journey. A prototype can use a provider’s test environment for payments or messages, but label that clearly. Before launch, replace test credentials through the correct access process and run a controlled live acceptance check. Do not describe a simulated integration as production-ready.
Example acceptance checklist for a booking MVP
One user can create a valid booking and retrieve it later. A second user cannot reserve the same resource at the same time. An unauthorised account cannot view the booking. A cancelled appointment does not trigger a reminder. Staff can find failed deliveries and take over. These checks connect interface quality with operational reliability.
Handover is part of the product
Record where the app runs, who owns the accounts, how to release an update, how data is backed up and where errors are reviewed. Separate development cost from hosting, usage and support. The next backlog should follow observed user friction; a working first release is a starting point for evidence, not proof that every assumption was right.