REST API Developers design, build, and maintain HTTP APIs that connect systems — internal microservices, third-party integrations, and partner platforms. In India, the role is split between two ecosystems: system integrators (TCS, Infosys, Wipro, HCL) where developers stitch enterprise backends with SAP, Salesforce, or banking core systems via APIs, and product companies (Razorpay, Cashfree, CRED, PhonePe, Setu) where developers build the public API layer that fintechs consume to power payments, banking, and credit flows. Day-to-day work covers OpenAPI 3.1 spec authoring, REST endpoint design (idempotency, HATEOAS, pagination, versioning), OAuth2/JWT authentication, API gateway configuration (Kong, Apigee, AWS API Gateway), Postman/Newman contract testing, webhook design, rate limiting, and Swagger UI hosting. Entry point is lower than general backend because the constraint set — HTTP verbs, status codes, JSON schema — is explicit and learnable, making this a practical first specialisation for developers coming from a services background.