Job Description: Backend Engineer (Blockchain Integration / REST API)Position Overview
We are hiring a Backend Engineer for a time-bound, private blockchain MVP. You will design and build the REST API layer that sits between web clients and a Hyperledger Fabric network: authentication, authorization, input validation, SDK-based chaincode invocation, and stable APIs for internal dashboards and public read-only endpoints.
This is a contract / project-based role with phased delivery. Project domain, client, and detailed specifications will be shared after NDA.
Role Summary
You will own the server-side application layer for a permissioned blockchain system. A separate Fabric engineer builds the network and chaincode; you integrate with it via the Fabric SDK, expose clean REST endpoints, enforce roles at the API level, and support frontend and QA during integration and release.
Strong API design, security discipline, and experience calling external systems (here: Fabric peers/orderers) are essential.
Key ResponsibilitiesAPI Design & Implementation
- Build a REST API in Node.js (Express/Fastify) or Go (Gin or similar)
- Implement endpoints for create, read, update/query, and transaction flows defined in project specifications
- Integrate with Hyperledger Fabric using the Node SDK or Go SDK (invoke writes, evaluate reads)
- Map API users to Fabric identities (certificates, MSP, or JWT claims → ledger identity)
- Provide a public read-only API for verification-style queries (unauthenticated, rate-limited)
- Produce OpenAPI (or equivalent) documentation for frontend and QA
Security & Authorization
- Implement authentication for protected routes (JWT, sessions, or agreed IdP pattern)
- Enforce role-based access control at the API layer (aligned with on-chain ACL rules)
- Validate and sanitize all inputs (IDs, UUIDs, dates, enums) before SDK calls
- Use HTTPS only; never store secrets or private keys in source control
- Integrate with a secrets vault pattern for certificates and credentials (AWS Secrets Manager, Azure Key Vault, or equivalent)
Integration & Reliability
- Work closely with the Fabric engineer on connection profiles, endorsement behavior, and error handling
- Implement consistent API error responses (400 invalid input, 403 unauthorized, 404 not found, 5xx with safe messages)
- Add logging (request ID, user/role, action, outcome — without sensitive payloads)
- Optional: caching for high-volume read/query endpoints where appropriate
- Support rate limiting on public endpoints
Testing & Delivery
- Write unit and integration tests for API routes and SDK integration
- Support end-to-end testing with frontend, chaincode, and QA
- Assist with performance validation (read/write latency targets per NFR spec)
- Contribute to deployment config (Docker, env vars, health checks) with DevOps
- Document setup, environment variables, and runbooks for handover
Required Qualifications
- 3+ years backend development experience
- Strong REST API design and implementation
- Production experience with Node.js or Go (state one primary stack in your application)
- Experience integrating with external services/SDKs (message queues, third-party APIs, or blockchain SDKs)
- Solid authentication & authorization implementation (JWT, sessions, RBAC)
- Strong input validation and API security practices
- Experience writing automated tests (unit + integration)
- Clear technical documentation and English communication for a distributed team
- Comfortable working from written specs (PRD, data model, API requirements) under NDA
Preferred Qualifications
- Direct experience with Hyperledger Fabric SDK (Node or Go) — invoke, query, wallet/identity management
- Experience on blockchain, supply chain, asset tracking, or regulated systems (details under NDA)
- AWS or Azure deployment (containers, API gateway, load balancers)
- Docker and basic CI/CD familiarity
- OpenAPI/Swagger for API contracts
- Familiarity with structured logging and observability (metrics, tracing, health endpoints)
- Understanding of permissioned blockchain concepts (channels, MSP, endorsement, commit flow)
Technical Environment (High Level)AreaStack / ExpectationAPIREST — Node.js or GoBlockchain integrationHyperledger Fabric via official SDKAuthJWT or session-based; role mapping to ledger identitiesFrontendWeb app (separate engineer) — consumes your APIBlockchain layerFabric network + chaincode (separate engineer)CloudMajor cloud provider (confirmed at kickoff)SecurityTLS, vault for secrets, API RBAC, rate limiting on public routes
Detailed endpoints, data models, and business rules are provided under NDA.
What You Will Deliver
By the end of the engagement:
- Production-quality REST API with documented endpoints
- Fabric SDK integration for all required invoke and query operations
- Authentication and role enforcement on protected routes
- Public read-only endpoints with rate limiting where specified
- Test coverage for critical API paths and error cases
- Deployment-ready service (containerized or as agreed) with configuration documentation
- Successful E2E flows through API → Fabric → response in staging/production-like environment
Milestones and acceptance criteria are defined in the statement of work.
What We Are Looking For
- Engineer who has shipped APIs used by real clients or internal products
- Comfortable owning integration complexity (SDK errors, timeouts, idempotency considerations)
- Security-minded: validation, authz, and secrets handled correctly by default
- Works well alongside a blockchain specialist without blocking on every ledger detail
- Pragmatic about MVP scope — core flows first, polish and hardening in later phases
Pay: ₹40,000.00 per month
Work Location: In person
