Context

A client needed a web application that could evolve with changing business rules and integrations without large rewrites. The goal was clear structure, testability, and predictable rollout of new features.

Architecture and patterns

We used a layered architecture with a clear API boundary, domain logic isolated from frameworks, and shared conventions for errors and validation. State and side-effects were confined to defined layers so behaviour was easier to reason about and test.

Feature flags and branch-by-abstraction allowed large changes to be developed and rolled out incrementally. Documentation focused on decisions, contract changes, and runbooks rather than low-level code comments.

Outcomes and lessons

Releases became more frequent and rollbacks were rare. Onboarding time for new developers dropped because responsibilities were clearly separated and patterns were consistent.

The main takeaway: investing in structure, testing, and deployment practices up front paid off as requirements and integrations grew. Small, consistent improvements in how the team worked mattered as much as any single technical choice.