Public Product APIs
Customer-facing APIs that drive partner integrations and developer adoption — versioned, documented with OpenAPI, with sandbox keys, code samples, and a developer portal.
API Development
REST, GraphQL & gRPC APIs Engineered for Real Production
We build production-grade REST, GraphQL, gRPC, and webhook APIs that your partners, mobile apps, and internal teams actually enjoy integrating with — versioned, documented in OpenAPI, secured with OAuth/JWT, rate-limited, observable, and SLA-backed in production.
OpenAPI 3.1 · OWASP-aligned · SLA-backed · Senior engineers
RESTGraphQL · gRPC · Webhooks
OpenAPI3.x specs by default
99.9%Uptime targets
100%OWASP-aligned
APIs We Build
From public product APIs that drive partner adoption to internal microservices that survive Black Friday — engineered with contracts, security, and observability from day one.
Internal Microservices APIs
Service-to-service APIs for distributed architectures — gRPC for performance, REST for ubiquity, with contracts, versioning policies, and idempotency keys for safe retries.
Third-Party Integrations
Robust integrations with Razorpay, Stripe, PayU, Shopify, Salesforce, Zoho, WhatsApp Business, SAP, Tally, and dozens more — with retries, deduplication, and reconciliation.
Webhook Systems
Outbound webhooks with HMAC signing, retry queues, replay protection, and dead-letter handling — so partners receiving your events trust them.
API Gateway & Auth Layer
API gateway design (Kong, AWS API Gateway, NGINX) with OAuth 2.1, JWT, mTLS, scoped API keys, rate limiting, and IP allow-listing — your security team can defend.
API Monetisation
Metered billing, plan-based quotas, overage handling, and Stripe billing wiring — turn your API into a revenue line, not just an integration tax.
Industries We Serve
APIs that power fintech, healthcare, retail, logistics, edtech, and enterprise integrations across India and global markets.
FinTech & BFSI
Healthcare
Retail & E-Commerce
Logistics
EdTech
Manufacturing
Real Estate
Professional Services
API Stack & Technologies
Polyglot stacks tuned to your hiring market and performance needs — Node, Python, Go, Java, and .NET, with modern gateways and OpenAPI tooling.
Node.jsRuntime
PythonRuntime
GoRuntime
Java / KotlinRuntime
.NET 8Runtime
NestJS / ExpressFramework
FastAPI / DjangoFramework
GraphQL Yoga / ApolloGraphQL
gRPC / ProtobufRPC
Kong / AWS API GWGateway
OAuth 2.1 / JWTAuth
OpenAPI 3.1Spec
Our API Development Process
A six-step contract-first delivery rhythm so consumers can mock and build alongside us — no surprises at integration time.
API Discovery & Contract
We map consumers, use cases, latency budgets, payload sizes, security posture, and rate-limit needs — then publish the OpenAPI / Protobuf contract for sign-off before code.
Resource & Schema Design
Resource modelling, pagination, filtering, error envelopes, idempotency, ETags — designed against the contract so your engineers and partners can mock and start consuming early.
Implementation
Senior-led builds with contract-first generation, request validation, structured error responses, audit logs, and exhaustive unit and integration tests.
Security & Performance
OAuth 2.1, scoped tokens, rate limiting, input sanitisation, OWASP API Top 10 hardening, load testing with k6/Locust, and DB query plan reviews.
Developer Portal & Launch
Hosted developer portal with OpenAPI docs, code samples, sandbox keys, and example flows — so partners go from signup to first call in under 10 minutes.
Observability & SLA Care
Metrics, traces, logs (Grafana / Datadog), uptime monitoring, incident playbooks, and SLA-backed support retainers — your API stays healthy after launch.
Why Choose Hendoi for APIs
Six commitments that decide whether your API becomes a platform — or just another endpoint your partners hate calling.
Contract-First, Always
OpenAPI 3.1 or Protobuf contracts published before code — so consumers can mock, validate, and start work in parallel with our build. No surprises at integration time.
OWASP API Top 10 Aligned
Auth, authorisation, input validation, rate limiting, secrets handling, and observability — all aligned to the OWASP API Security Top 10. Defensible to your security team.
Performance Validated
Load tested with k6 or Locust against realistic traffic shapes before launch. DB query plans reviewed. P95 latency targets agreed upfront and tracked in production.
Docs Developers Love
Hosted developer portal, OpenAPI-generated reference, runnable code samples, sandbox keys, and an integration guide that your partners actually finish.
Senior Engineering Only
Architecture is reviewed by Sundarapandi Muthupandi (CEO). You get judgement on versioning, idempotency, and contract evolution — not just CRUD code.
SLA-Backed Care
Post-launch retainers with response-time SLAs, incident playbooks, and on-call rotations. Your API does not get abandoned the day after go-live.
Engagement Models
Pick the commercial shape that matches where your API programme actually is — greenfield, evolving platform, or legacy modernisation.
Greenfield API Build
Fixed-scope build of a new REST/GraphQL/gRPC API with OpenAPI docs, developer portal, sandbox keys, and a 30-day hypercare window for partner onboarding.
- OpenAPI 3.1 contract
- Developer portal + sandbox
- 30-day hypercare
API Platform Squad
A senior squad — backend, security, DevOps — building, hardening, and evolving your API platform with weekly demos, transparent burn, and SLA-backed support.
- Senior backend + security
- Weekly demos & sprint planning
- SLA-backed on-call
API Audit & Modernisation
A 4-week audit covering security, performance, versioning, and developer experience — followed by a prioritised modernisation roadmap and execution sprint.
- OWASP API Top 10 audit
- Performance + cost review
- Prioritised remediation plan
Real-World Use Cases
Representative API platforms engineered across NBFC, D2C, healthcare, logistics, edtech, and payment use cases.
NBFC Loan Origination API
REST API exposing loan origination, KYC, bureau pulls, and disbursement to partner channel sales — with idempotency keys, retry-safe webhooks, and full audit trails for RBI inspections.
D2C Inventory Sync API
GraphQL API syncing inventory and orders across Shopify, marketplaces, and an internal warehouse system — with conflict resolution and reconciliation reports.
Hospital EMR Integration
REST + webhook integrations between an in-house EMR and lab, pharmacy, and billing partners — with HIPAA-aware logging and patient-data redaction in error responses.
Logistics Track-and-Trace API
Public-facing API for shipment tracking with rate-limited free tier and metered enterprise tier — partner companies pay per call via Stripe billing.
EdTech Content Delivery API
GraphQL API powering an EdTech mobile app and admin web — pagination, role-based field-level security, and analytics events captured per query.
Payment Gateway Aggregator
Unified API that abstracts Razorpay, PayU, Stripe, and PhonePe behind a single contract — with intelligent routing, retries, and reconciliation jobs for finance teams.
Frequently Asked Questions
Common questions tech leaders ask before committing to a new API platform.
Should I build a REST, GraphQL, or gRPC API?
REST for public APIs and partner integrations (broadest tooling support). GraphQL when you have mobile and web clients with very different data needs and want to reduce over-fetching. gRPC for internal service-to-service traffic where latency, payload size, and strong contracts matter. We help you choose during discovery and document the trade-offs.
How do you handle API versioning?
We default to URI-based versioning for REST (v1, v2), strict additive evolution for GraphQL schemas, and Protobuf-versioned services for gRPC. Deprecation calendars are published in advance, with consumer migration support and backwards compatibility windows we agree upfront.
How is API security handled?
OAuth 2.1 with PKCE for user-facing flows, JWT or opaque tokens for service-to-service, mTLS for high-security pairs, scoped API keys for public APIs, rate limiting per key/IP, input validation, and full OWASP API Top 10 alignment. We document the threat model.
What does API monetisation look like?
Per-request metered billing, plan-based quotas, overage handling, and Stripe billing wiring. We can build a developer portal with self-service plan upgrades, usage dashboards, and invoices — turning the API from a cost into a revenue line.
How do you document APIs?
OpenAPI 3.1 specs published in code via decorators or pydantic-style annotations, rendered as an interactive developer portal with try-it-out functionality. We also generate SDKs (TypeScript, Python, Go) from the spec when partner integrations need it.
Can you take over an existing API?
Yes. We baseline performance, security posture, error rates, and developer experience, then deliver a prioritised modernisation roadmap. Common work includes adding OpenAPI docs, hardening auth, fixing N+1 queries, and introducing structured logging.
How long does an API project take?
A focused product API typically takes 8-14 weeks from contract to launch. A larger platform with monetisation, developer portal, and multi-tenant features can run 4-6 months. We share a milestone plan with weekly demos.
What about webhooks for outbound events?
We build production-grade webhook systems with HMAC signing, exponential-backoff retries, dead-letter queues, replay endpoints for partner debugging, and a delivery dashboard so partners can self-service investigate failures.