System Discovery & Backend Rebuild
Recovered what an undocumented production system actually did, specified it, and rebuilt the backend against that specification — delivered for an enterprise client through Q Agency.
- Starting point
- Undocumented system
- Scope
- Recover · specify · rebuild
The problem
Replacing part of a system that has been running for years means first answering a question nobody can answer from the documentation: what does it actually do? Documented behaviour and real behaviour diverge over time, and the gaps are exactly where the risk sits — the undocumented edge case that some downstream process has quietly depended on for years. Rebuild against the documentation and you ship a system that is correct according to a description nobody has validated.
The approach
Delivered the discovery and backend work for one of Q Agency’s enterprise clients, in that order deliberately:
- Behaviour recovery first, establishing what the existing system really did before changing any part of it — the prerequisite for replacing anything safely.
- Specification from observation, writing the recovered behaviour down so there was something concrete to build against and test against, rather than a shared assumption.
- Backend rebuilt against the specification, not against what the old system was supposed to have been doing.
The outcome
The client got a backend built on a validated understanding of its own predecessor — and they kept the specification, which is the part that stays useful long after the migration is finished.