REST (Representational State Transfer) uses HTTP verbs and resource-oriented URLs as the lingua franca of web APIs. Stateless, cacheable, and layered — REST's uniform interface constraint enables universal interoperability across the networked world.
GraphQL replaces multiple REST endpoints with a single typed schema. Clients declare exactly the data shape they need — over-fetching and under-fetching disappear. Resolvers connect schema fields to data sources with fine-grained control.
gRPC uses HTTP/2 multiplexing and Protocol Buffer binary serialization for high-performance service-to-service communication — 5-10x smaller payloads and 10x faster serialization than JSON REST at the cost of human readability.
OpenAPI 3.1 defines a machine-readable API contract — endpoints, schemas, security, examples — enabling auto-generated clients, server stubs, documentation, and mock servers. The API contract is the source of truth for the entire integration surface.
The API gateway is the unified entry point for all client traffic — handling authentication, rate limiting, routing, load balancing, observability, and protocol translation across a heterogeneous backend microservice landscape.
P50/P95/P99 latency percentiles, error rate histograms, and distributed traces across the API call graph provide the observability layer for understanding real-world API performance and identifying degradation before users notice.
The architects, researchers, and practitioners who shaped the APIs that run the modern web.
Core vocabulary for API design, protocol selection, and interface architecture.