API Design and Versioning 
Building Interfaces You Won't Regret 

An API is the one part of your system you can never quietly refactor. The moment a customer or another team writes code against it, its shape becomes a contract you're on the hook to honor — and every awkward field name, inconsistent error, or half-thought-through pagination scheme becomes a liability you carry for years. Good API design is not about cleverness; it's about making the obvious thing correct, keeping the whole surface consistent, and giving yourself a way to change your mind later without breaking everyone who trusted you. Teams that get this right ship integrations in days and rarely field support tickets about the API itself. Teams that don't spend the next three years apologizing in changelogs.

Design for the integrator, not the database

The most common failure is exposing your database schema as your API — endpoints that mirror tables, fields named for internal columns, and responses that leak implementation details you'll want to change. Design instead around the resources and actions your consumers actually think in terms of, and keep them consistent: the same casing everywhere, the same shape for every error, timestamps in ISO 8601 with timezones, money as integer minor units rather than floats, and identifiers that are opaque strings rather than sequential integers that leak volume and invite enumeration. Consistency is worth more than any individual clever decision, because it lets an integrator learn your API once and predict the rest of it. Small things compound: a single inconsistent plural or a boolean that's sometimes a string is the kind of paper cut that erodes trust in the whole surface.

Pagination, filtering, and the defaults that bite later

The endpoints that return lists are where APIs quietly fall over at scale, so decide these up front rather than retrofitting them under load. Never return an unbounded collection — always paginate, and prefer cursor-based pagination over offset for anything that changes, because offset pagination silently skips and repeats rows as the underlying data shifts and gets slower the deeper you go. Bake in a sane default page size and a hard maximum so a single caller can't ask for a million rows and take your database with them. The same discipline applies to filtering and sorting: expose a small, explicit set of filterable fields backed by indexes rather than letting callers query on anything, which is how you end up with full table scans in production. These defaults are nearly impossible to tighten later without breaking someone, so choose the conservative option now.

Versioning: how to change your mind safely

You will need to make breaking changes, so the real question is how you absorb them without a coordinated flag-day migration across every customer. The pragmatic default is a version in the URL path (`/v1/`, `/v2/`) — it's ugly to purists but trivially visible in logs, easy to route, and unambiguous to the integrator, which beats header-based versioning's elegance in every practical way. The more important discipline is to make breaking changes rare: adding a field, a new endpoint, or an optional parameter is non-breaking and needs no new version, so version only when you must remove or change the meaning of something. When you do cut a new version, run old and new in parallel rather than forcing an instant cutover, and treat a version as a promise about compatibility, not a chance to redesign everything at once. Most well-run APIs live on `/v1/` for years precisely because their owners are strict about what counts as breaking.

Deprecation is a process, not an announcement

Retiring an old version or field is where APIs generate their worst customer pain, almost always because deprecation was treated as a single email rather than a managed lifecycle. Announce the change with a real timeline, not 'soon'; emit a `Deprecation` header and log usage so you can see who is actually still calling the old path; and reach out to the specific integrators who haven't migrated instead of assuming the blog post was read. Give enterprise customers more runway than you think you need — their change windows are measured in quarters — and never delete an endpoint while meaningful traffic still flows to it. The goal is that a deprecation surprises no one, because the alternative is a customer's production system breaking on a Monday and a very hard conversation about why you didn't tell them.

Contracts and tests are what keep it honest

A written spec is what turns all of this from good intentions into something enforceable. Describe the API in OpenAPI and treat that document as the source of truth — generate docs, client SDKs, and server stubs from it so the spec and the implementation can't quietly drift apart. Add contract tests that fail your build the moment a response stops matching the schema, which is what actually catches the accidental breaking change before it ships rather than after a customer reports it. Pair that with good observability on the live API — per-endpoint latency, error rates, and version usage — so you know how the contract behaves in production and which parts are safe to evolve. An API you can't test against a contract is one you'll be afraid to change, and an API you're afraid to change ossifies.

How Infiniti Tech Partners designs APIs

We design APIs from the integrator's point of view, not the database's: consistent naming and errors, cursor pagination and sane limits baked in from day one, and opaque identifiers that don't leak your internals. We keep breaking changes rare by being strict about what 'breaking' means, version in the path when we genuinely must, and run old and new in parallel with a real deprecation process rather than a flag-day cutover. Every API we build ships with an OpenAPI contract, generated clients, contract tests wired into CI, and per-endpoint observability so the interface can evolve safely instead of ossifying. The result is an API integrators adopt quickly and you're not afraid to change — which, over a product's life, is worth far more than any single elegant endpoint.