API & Integration Development — REST, GraphQL, gRPC & Microservices

REST is the most widely adopted API style — resource-oriented, stateless, and simple to consume from any HTTP client. It's the right default for public APIs and most web application backends. GraphQL lets clients specify exactly which fields they need in a single request — ideal for frontend-heavy applications where over-fetching wastes bandwidth and under-fetching requires multiple round-trips. gRPC uses Protocol Buffers and HTTP/2 for high-performance binary communication — best for internal microservice-to-microservice calls where low latency and strongly typed contracts matter more than broad compatibility. We recommend based on your specific use case: public developer API, mobile frontend, or internal service mesh.

Legacy systems without API surfaces are common — COBOL mainframes, RPG applications, older SAP or Oracle installations, and monolithic .NET WebForms applications all fall into this category. We build API adapters and facades that sit in front of the legacy system: reading and writing data through existing database interfaces, screen-scraping adapters, file-based interchange, or direct library calls depending on what's accessible. The result is a modern REST or GraphQL API over the legacy system that modern applications can consume — without touching the legacy code that your business depends on.

API security is layered. At the transport level, TLS 1.3 everywhere. At the authentication level, we implement OAuth 2.0 with JWT access tokens for user-context APIs, API keys with scoped permissions for machine-to-machine integrations, and mTLS (mutual TLS) for internal microservice communication in high-security environments. At the authorisation level, role-based access control (RBAC) or attribute-based access control (ABAC) enforced at the API gateway before requests reach the application. We also implement rate limiting, IP allowlisting, request signing for webhooks, and API threat protection (injection, schema validation) at the gateway layer.

Event-driven architecture (EDA) decouples systems by having producers emit events to a message broker (Kafka, RabbitMQ, SQS) and consumers process those events independently. Unlike synchronous REST APIs where the caller waits for a response, EDA is asynchronous — the producer doesn't care when or how the event is processed. Use EDA when you need real-time data propagation across multiple systems, when you need to handle traffic spikes gracefully, when you need a reliable audit trail of everything that happens, or when you want to add new consumers (new integrations, new analytics pipelines) without changing the producer. The complexity trade-off is real: EDA requires message schema governance, dead-letter queues, idempotent consumers, and ordering guarantees that synchronous APIs handle automatically.

API versioning strategy depends on the type of API and its consumers. For public or partner APIs with external developers, we use URL-based versioning (/v1/, /v2/) with a documented deprecation policy and at least 12 months of parallel support. For internal APIs within your own system, header-based versioning or content negotiation is cleaner. For event schemas in Kafka-based systems, we use a schema registry (Confluent Schema Registry or AWS Glue) that enforces backward compatibility checks before new schemas are deployed. The underlying principle is: additive changes (new fields, new endpoints) are always backward compatible; breaking changes (removing fields, changing types) require a new version with a migration path.

Yes — developer portals are a standard deliverable for API platform engagements. We build developer portals using Redoc, Docusaurus with custom API reference rendering, or dedicated platforms like Stoplight or readme.com depending on the audience and maintenance model you prefer. A production developer portal includes: interactive API reference generated from your OpenAPI spec, authentication and API key management, usage examples in multiple languages, sandbox environment with mock data, a changelog tracking breaking and non-breaking changes, and search. For businesses monetising their API as a product, we also build rate limiting tiers, usage dashboards, and self-service subscription management.