API Development

Custom API development that scales

We design and build robust, secure, and documented REST and GraphQL APIs. From OpenAPI specification to production deployment with authentication, rate limiting, and versioning. Your backend ready to connect with any frontend, mobile app, or external system.

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The challenge

A poorly designed API slows your product. A well-designed API multiplies it.

APIs are the backbone of every modern digital product. Every architectural decision (REST vs GraphQL, authentication model, versioning strategy, response format) directly impacts development velocity, integrator experience, and system scalability. An API that is not well designed from the start generates exponential technical debt.

Custom API development goes far beyond exposing endpoints. It requires thinking about clear contracts with OpenAPI/Swagger specifications, secure authentication with JWT or OAuth2, rate limits to protect the system, semantic versioning to evolve without breaking existing integrations, and interactive documentation that allows developers to integrate in minutes, not days.

The API-first paradigm fundamentally changes how products are built. Instead of designing the interface and adapting the backend, you first define the API contract and then build all layers on top. This allows frontend, mobile, and third-party teams to work in parallel from day one. Companies that adopt API-first reduce development time by 30% to 50% based on our experience across 150+ projects.

At Soamee, we have designed APIs that process millions of daily requests. From the digital certification API for eEvidence, requiring legal traceability for every operation, to the advertising data API for InfoAdex, serving analytical queries over 55 million records. Through the integration API for Cawa, connecting brands with content creators in real time. Each API has different requirements, but all share the same design principles: consistency, security, performance, and impeccable documentation.

REST

RESTful API standard

GQL

Flexible GraphQL

Auth

JWT / OAuth2

Docs

Auto-generated OpenAPI

Key capabilities

What every API development project includes

Every API we build follows a rigorous process of design, implementation, testing, and documentation.

API-First Design with OpenAPI

We define the API contract before writing code. Complete OpenAPI 3.1 specifications with data models, endpoints, parameters, error responses, and examples. Automatic code generation for SDKs in TypeScript, Python, and other languages. Request and response validation against the schema to guarantee consistency.

REST API and GraphQL

RESTful APIs with coherent resource design, semantic HTTP methods, cursor-based pagination, advanced filtering, and HATEOAS. GraphQL with schema-first design, optimized resolvers, DataLoader to avoid N+1 queries, and subscriptions for real-time data. We choose the right paradigm for your use case.

Authentication and authorization

We implement JWT with refresh tokens, OAuth2 with authorization code and client credentials flows, API keys for server-to-server integrations, and HMAC signatures for webhooks. Granular Role-Based Access Control (RBAC). Rate limiting per user, per tenant, or per endpoint. IP whitelisting and mutual TLS for enterprise clients.

Rate limiting and protection

Configurable rate limiting with token bucket or sliding window algorithms. Throttling by client tier (free, pro, enterprise). Abuse protection with anomaly pattern detection. Circuit breakers for external dependencies. Retry policies with exponential backoff. Standard 429 responses with Retry-After headers.

Versioning and evolution

Versioning strategies that allow evolving the API without breaking existing integrations. URL versioning (/v1/, /v2/) or header-based. Deprecation policies with clear transition periods. Automated changelog. Feature flags for gradual rollout of new functionality.

Testing and documentation

Automated testing with full coverage: unit tests, integration tests against real databases, contract tests with Pact, and load tests with k6 or Artillery. Interactive documentation with Swagger UI or Redoc. Auto-generated Postman collections. Developer portal with quick-start guides, tutorials, and code snippets.

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Technologies

API development tech stack

Production-proven tools and frameworks for building high-performance APIs.

Node.js NestJS Express FastAPI Python TypeScript GraphQL Apollo Server Prisma PostgreSQL MongoDB Redis OpenAPI 3.1 Swagger UI JWT OAuth2 Docker Kong Postman k6

Results

Numbers that back our APIs

<100ms

Average p95 latency

APIs optimized with smart caching, efficient queries, and correct indexing for ultra-fast responses.

99.99%

Production uptime

Resilient architecture with health checks, circuit breakers, and zero-downtime deployments.

150+

Projects delivered

Accumulated experience in APIs for SaaS platforms, marketplaces, mobile apps, and enterprise integrations.

How we work

From specification to production endpoint

A structured process that guarantees consistent, secure, and documented APIs.

API contract design

We define resources, endpoints, data models, authentication, and errors. We deliver the complete OpenAPI specification validated with stakeholders before writing any code.

Implementation and testing

Iterative development with TDD. Every endpoint includes unit tests, integration tests, and contract tests. Mandatory code reviews and CI/CD with automatic validation against the OpenAPI spec.

Security and performance

Security audit with OWASP API Top 10. Load testing with k6 to validate performance under load. Rate limiting, caching, and query optimization until defined SLAs are met.

Documentation and launch

Developer portal with interactive documentation, quick-start guides, and SDKs. Zero-downtime deployment, monitoring with alerts, and continuous post-launch support.

Case studies

Production APIs we have built

Real projects where API design was a critical piece of success.

eEvidence

Digital certification platform with enterprise API for massive integration of electronic evidence with legal validity. OAuth2 authentication, webhooks, and SDKs.

Digital certification API

Cawa

Social commerce engine with integration API to connect brands with content creators. REST API with tiered rate limiting and OpenAPI documentation.

Social commerce API

InfoAdex

Advertising data API serving analytical queries over 55 million records. GraphQL for flexible queries and optimized pagination.

55M+ records queryable via API

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FAQ

Frequently asked questions about API development

REST API or GraphQL: which is better for my project?

It depends on the use case. REST is ideal when you have well-defined resources with standard CRUD operations, need efficient HTTP caching, or your consumers are diverse (mobile apps, third parties, IoT). GraphQL shines when clients need flexibility to request exactly the data they need, when you have interfaces combining data from multiple sources, or when you want to avoid over-fetching/under-fetching. In many projects, we use REST for the public API and GraphQL for the internal frontend. They are not mutually exclusive.

How much does custom API development cost?

The range varies based on complexity. A simple REST API with 10-15 endpoints, JWT authentication, and OpenAPI documentation can cost between EUR 8,000 and 20,000. A complete API with GraphQL, OAuth2, tiered rate limiting, webhooks, SDKs, and a developer portal ranges from EUR 30,000 to 80,000. Enterprise APIs with high-availability requirements, multi-region deployment, and security certifications can exceed EUR 100,000. We always recommend starting with core endpoints and expanding in iterations based on real usage.

How is the API documented?

Every API includes auto-generated OpenAPI 3.1 documentation with Swagger UI or Redoc as the interactive interface. We also generate Postman collections for manual testing, SDKs in major languages, quick-start guides with code examples, and a changelog with each version. For public APIs, we build a complete developer portal with authentication, testing sandbox, and usage metrics.

How is API versioning managed?

We implement semantic versioning with support for multiple active versions simultaneously. Breaking changes are only introduced in major versions (v1 to v2), with a deprecation period of at least 6 months. Backward-compatible changes (new fields, new endpoints) are added without version changes. Each version has independent documentation, and we notify integrators before deprecating any endpoint.

What security do the APIs have?

All APIs include mandatory HTTPS, JWT or OAuth2 authentication, rate limiting, input validation against schema, and protection against OWASP API Security Top 10 vulnerabilities. For enterprise APIs, we add mutual TLS, IP whitelisting, audit logs for every request, anomaly detection, and automatic attack response. We perform periodic pen testing and security review with every release.

Let's start

Let's design your API together

Tell us what systems you need to connect. Within 24 hours, you will receive a proposal with architecture, endpoints, and timeline. No commitment.

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