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API Development Services for Partner and Public Integrations

We design, build, document and version REST and GraphQL APIs so partners can integrate without asking your engineers for help.

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How we work

An API called only by your own frontend can stay undocumented and inconsistent. One that a partner, a mobile team or an outside developer builds against cannot. It needs a contract that changes only with notice, authentication that scopes access correctly, rate limits that protect uptime, and documentation clear enough for a developer who has never spoken to your team to build against it correctly on the first attempt.

We design the contract before writing implementation code: resources, endpoints, request and response shapes, error formats and versioning strategy, captured in an OpenAPI specification or a GraphQL schema. Authentication is built around OAuth 2.0 scopes matched to what each partner actually needs, rate limiting is tuned to protect the system without blocking legitimate traffic, and a gateway sits in front to handle routing, throttling and logging in one place.

This is API-first work: the contract, the auth model and the versioning plan, not the server-side business logic behind it (see backend development) or the interface consuming the API (see frontend development).

What we deliver

API Development services

  • REST API Design and Build

    Resource modeling, endpoint design and consistent request and response formats, built from an OpenAPI specification agreed on before implementation starts.

  • GraphQL API Development

    A GraphQL schema over your existing services when clients need to fetch related data in one request instead of chaining multiple REST calls, with query depth limits to prevent abuse.

  • OpenAPI Specification and Documentation

    A versioned OpenAPI spec that generates interactive documentation, example requests and client SDKs automatically, so it stays accurate as the API changes.

  • Authentication and Authorization

    OAuth 2.0 flows scoped to what each client actually needs, API key management for simpler cases, and token expiry and rotation handled correctly from the start.

  • Rate Limiting and Quota Management

    Per-client rate limits and quotas tuned by endpoint cost, with clear response headers so a well-behaved client knows exactly how close it is to its limit.

  • API Gateway Setup

    A gateway layer handling routing, throttling, authentication checks and request logging in one place, instead of duplicating that logic across every service.

  • Versioning and Deprecation Strategy

    A documented approach to shipping breaking changes without breaking existing integrations: version headers or URL versioning, deprecation notices and a defined sunset window.

  • Third-Party and Partner Integrations

    Integration with payment processors, shipping carriers, CRM platforms and other external APIs your system needs to call, with retry and error handling for when they fail.

You receive

Deliverables

  • A versioned OpenAPI specification or GraphQL schema
  • Working authentication with OAuth 2.0 or scoped API keys
  • Rate limiting and quota configuration by client tier
  • Interactive API documentation generated from the spec
  • Postman collection or SDK examples for partner developers
  • Monitoring dashboards for error rates, latency and usage by endpoint

How we work

Our api development process

  1. Contract-First API Design

    We design the resources, endpoints and data shapes as a specification first, so partners and internal teams can review the contract before any code is written.

  2. Auth and Rate Limit Planning

    Authentication scopes and rate limit tiers are defined against real client use cases, not a generic default that turns out to be too strict or too loose.

  3. Build and Automated Testing

    The API is built against the agreed contract with automated tests that catch a response shape change before it reaches a partner's integration.

  4. Documentation and SDK Generation

    Documentation and example clients are generated from the same specification that defines the API, so they can't drift out of sync with the actual behavior.

  5. Partner Sandbox and Feedback

    A sandbox environment with test data lets partners integrate and raise issues before the API is locked into a versioned production release.

  6. Versioned Production Release

    The API ships with a version number and a deprecation policy already documented, so future changes have a defined path that doesn't break existing clients overnight.

Designing an API Contract Before Writing Code

The cheapest time to fix an API's shape is before anyone has built against it. We write the OpenAPI specification or GraphQL schema first and review it with whoever will consume it, whether that's a partner developer, a mobile team or another group inside your own company.

This catches the expensive mistakes early: a resource that's missing a field a client actually needs, an inconsistent error format across endpoints, a pagination approach that won't scale past a thousand records. Fixing those in a document costs an hour. Fixing them after three partners have integrated costs a migration plan.

Versioning Without Breaking Existing Integrations

Every API eventually needs a breaking change, and the question is whether existing integrations find out from a deprecation notice or from a production error. We version explicitly, either through the URL or a header, and document a sunset window before an old version stops working.

Smaller changes that don't break existing clients (adding an optional field, a new endpoint) don't need a version bump at all. Reserving versioning for genuine breaking changes keeps the version number meaningful instead of incrementing on every deploy.

Rate Limiting That Protects Uptime Without Blocking Real Usage

A rate limit set too loose doesn't protect anything. Set too tight, it throttles a legitimate partner running a normal workload. We tune limits by endpoint cost (a search query and a simple lookup shouldn't share a quota) and by client tier, and return clear headers showing remaining quota so a well-built client can back off gracefully instead of hitting a wall.

  • Per-endpoint limits based on actual computational cost
  • Per-client tiers for partners with different traffic needs
  • Response headers showing remaining quota and reset time
  • Gateway-level enforcement so limits apply consistently across services

Technology

Technologies we use

Industries

API Development by industry

Solutions

Systems we build with this service

Budget

What drives cost and timeline

  • Number of endpoints and resources

    A narrow API with a handful of resources is a smaller project than one exposing your full data model to outside consumers.

  • Authentication complexity

    A single API key is simpler to implement than a full OAuth 2.0 flow with multiple scopes and per-partner permission tiers.

  • Expected partner traffic

    Rate limiting, caching and gateway sizing decisions change depending on whether you expect ten integrations or ten thousand requests a second.

  • Public developer portal needs

    A polished, self-serve documentation site with interactive testing costs more to build than internal documentation for a known set of partners.

  • Third-party integration count

    Each external system your API needs to call (payments, shipping, CRM) adds its own error handling, retry logic and testing surface.

Get a free estimateSee engagement models

Compliance

Standards we design and build to

None of these is a certification or attestation held by this agency. They are the standards we design and build client systems to, so your own audit or assessment starts from a sound base.

  • GDPR / UK GDPR

    Personal data handled on a lawful basis, with data minimisation and a documented retention policy.

  • HIPAA safeguards

    Administrative, physical and technical safeguards applied where a system touches protected health information.

  • PCI DSS scope reduction

    Card payment flows tokenised through a certified processor so cardholder data never touches your systems.

  • SOC 2 readiness

    Access control, change management and audit logging built in from day one, ready for a client's own SOC 2 audit.

  • WCAG 2.2 AA

    Keyboard navigation, colour contrast and screen-reader labelling checked against the AA success criteria.

  • OWASP ASVS

    Authentication, session handling and input validation reviewed against the Application Security Verification Standard.

We list certifications only when they are real and current. See our security practices →

FAQ

Questions about API Development

Do you build both REST and GraphQL APIs, or should we pick one?

Most systems benefit from REST for straightforward resource access and GraphQL where clients need to combine related data in one request, such as a mobile app avoiding several chained calls. We'll recommend one, the other, or both layered together based on how your clients actually query the data.

How do you version an API without breaking partners already integrated with it?

We version explicitly through a URL path or header, keep the previous version running through a documented sunset window, and reserve version bumps for genuine breaking changes. Additive changes, like an optional new field, ship without a version change at all, so partners aren't forced to update for no reason.

Can you add OAuth 2.0 to an API that currently only checks a static key?

Yes. We introduce OAuth 2.0 alongside the existing key-based auth during a transition period, so current integrations keep working while new and updated clients move to scoped tokens. The cutover timeline depends on how many existing integrations need to migrate.

How do you decide on rate limits for a public API?

We look at the actual computational cost of each endpoint (a full-text search costs more than a simple lookup) and set tiers based on expected traffic per client type. Limits ship with clear response headers so well-built clients can see their remaining quota and back off before hitting a hard wall.

Can you turn our internal API into a documented public one partners can self-serve against?

Yes, though it usually means adding things an internal API never needed: consistent error formats, versioning, a rate limiting layer and documentation generated from a specification rather than tribal knowledge. We audit the current API first to see how much of that groundwork already exists.

Do you generate SDKs for partners in different languages?

We can generate client SDKs directly from the OpenAPI specification for common languages, which keeps them in sync with the actual API automatically. For partners with specific requirements beyond the generated client, we can also hand-write a thin wrapper library.

Price your api development project

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