Software Engineering on Nalar

Contract Tests for Reliable Service Boundaries

Tue, 01 Sep 2026 00:00:00 +0700

Distributed systems fail in an awkward place: each service can pass its own tests while the interaction between two services is incompatible.

A provider may rename a JSON field, tighten validation, change an enum, or stop returning a value that a consumer quietly depends on. Contract tests make those cross-service assumptions executable.

What a contract is

A contract describes an observable interaction between a consumer and a provider.

For an HTTP API, it might specify:

Evolving APIs Without Breaking Clients

Tue, 01 Sep 2026 00:00:00 +0700

An API is not only an HTTP path or function signature. It is a contract about syntax, semantics, timing, errors, ordering, defaults, and lifecycle.

Breaking changes often happen because a server remains syntactically compatible while changing one of those less-visible assumptions.

Safe API evolution starts by identifying what clients can reasonably depend on and designing changes that allow old and new versions to coexist.

Compatibility has multiple dimensions

A change can preserve JSON shape and still break clients.

Feature Flags Without Long-Lived Technical Debt

Tue, 01 Sep 2026 00:00:00 +0700

Feature flags decouple code deployment from feature release. A team can deploy dormant code, enable it for internal users, roll it out gradually, and disable it without rebuilding the application.

The cost is hidden control flow. Every long-lived flag creates another possible system configuration, and interacting flags multiply those configurations quickly.

The engineering goal is therefore not “use flags everywhere.” It is to make each flag temporary, observable, and owned.