API Development and Integration Services
Custom REST and GraphQL API development plus third-party integrations — payments, CRM, ERP, logistics. Secure, documented, versioned, and built to scale.
Get a Free Quote →API Development and Integration Services
Every modern product is a network of systems talking to each other — your app, your payment gateway, your CRM, your logistics partner. V2S Infosystem Private Limited designs, builds, and integrates the APIs that connect them, so data moves automatically instead of getting re-typed by hand.
Get a Free QuoteWhat Is API Development and Integration?
API development is building a well-documented, secure interface that lets other software — your own mobile app, a partner's system, or a third-party SaaS tool — read and write data from your platform in a controlled way. Integration is the other half: wiring your systems up to APIs that already exist, like Stripe for payments, Salesforce for CRM, or a shipping carrier's tracking API.
The custom API development market was valued at roughly $3.5 billion in 2024 and is projected to grow to over $10 billion by 2033 — driven almost entirely by businesses realizing that manual data entry between disconnected systems doesn't scale, and every hour spent copy-pasting data between tools is an hour a competitor with real-time integrations doesn't spend.
Done well, an API is more than an endpoint that returns JSON — it needs authentication, rate limiting, versioning, error handling, and documentation that a developer who has never spoken to your team can pick up and use correctly on the first try.
Problems We Solve
Manual Data Re-Entry
Staff copying order data from your app into your accounting system every day — a direct integration eliminates this entirely.
No API for Partners
Enterprise clients and partners increasingly require an API before they'll integrate with you at all — without one, you're excluded from deals.
Over-Fetching / Under-Fetching
A REST API returning too much or too little data per call slows mobile apps down — GraphQL or a better-designed REST schema fixes this.
Unsecured or Undocumented Endpoints
APIs built as an afterthought often lack proper auth, rate limiting, or versioning — a security and stability risk as usage grows.
Disconnected SaaS Tools
Your CRM, payment processor, and support desk don't talk to each other, forcing your team to check three dashboards for one customer's story.
Breaking Changes on Third-Party APIs
A partner API updates without warning and your integration silently breaks — we build monitoring and fallback handling so you find out before your customers do.
What We Build
From a single webhook to an enterprise-scale API gateway serving thousands of partner requests per minute.
Custom REST APIs
Resource-based, versioned, documented with OpenAPI/Swagger, with proper pagination, filtering, and consistent error responses.
GraphQL APIs
Single-endpoint, client-driven queries for mobile apps and dashboards that need flexible, efficient data fetching with fewer round-trips.
Webhooks & Event Streaming
Push data out the moment something changes — order placed, payment received, status updated — instead of forcing partners to poll.
Payment Gateway Integration
Razorpay, Stripe, PayPal, and India-specific rails (UPI, BBPS) integrated with proper reconciliation and webhook-based status updates.
CRM & ERP Integration
Salesforce, HubSpot, Zoho, SAP, and custom ERP systems synced bidirectionally so no team works from stale data.
API Gateway & Rate Limiting
A single managed entry point handling authentication, throttling, request logging, and routing across multiple backend services.
Common Integration Patterns We Support
Synchronous request/response — your system calls a partner API directly and waits for a reply, used when the caller needs an immediate answer (e.g. checking payment authorization before confirming an order).
Asynchronous webhooks — the third-party system notifies you the moment something changes (a payment clears, a shipment updates) instead of you polling for status on a timer, which is both faster and cheaper on API rate limits.
Batch/scheduled sync — for systems without real-time APIs, or where near-real-time is good enough, we run scheduled jobs that reconcile data on a fixed interval with conflict-resolution rules for records changed on both sides.
Message queue-based integration — for high-volume systems, we decouple producers and consumers with a message queue (RabbitMQ, Azure Service Bus) so a slow or temporarily unavailable downstream system doesn't block the rest of your platform.
Our Process
Requirements & Data Mapping
We map exactly which data needs to flow where, at what frequency, and identify every system that needs to be touched.
API Design & Schema Contract
Endpoints, resources, and payloads are designed and reviewed with you before a single line of implementation code is written.
Build with Auth, Rate Limiting & Versioning
Every API ships with OAuth2/API-key authentication, request throttling, and a versioning scheme so future changes never break existing consumers.
Integration Testing Against Real Endpoints
We test against sandbox and, where possible, production-mirrored environments of every third-party system involved, including failure and retry scenarios.
Documentation & Monitoring
You get OpenAPI/Swagger docs a third-party developer can use unassisted, plus uptime and error-rate monitoring so issues are caught before they escalate.
Typical Pricing Ranges (2026)
| Project Type | Typical Range |
|---|---|
| Simple CRUD API (single resource, basic auth) | $15,000 - $40,000 |
| Medium REST API (20-50 endpoints, complex logic) | $40,000 - $120,000 |
| GraphQL API with custom resolvers | $10,000 - $150,000+ |
| Single third-party integration (one service) | $290 - $490 setup, or $1,500 - $4,000 for a full data-sync connection |
| Enterprise API gateway, multi-partner integrations | $150,000 - $500,000 |
Ranges reflect current 2026 industry benchmarks for the global custom API development market; your actual quote depends on the specific systems, data volume, and compliance requirements involved.
Why Integrations Fail Without Expert Design
Most broken integrations don't fail on day one — they fail three months later, when traffic grows, a partner API changes its response format without warning, or an edge case (a refund, a partial shipment, a currency mismatch) that nobody tested for shows up in production. A DIY integration built by a generalist developer often has no retry logic, no idempotency handling, and no monitoring — so the first sign of trouble is a customer complaint, not an alert.
We design every integration assuming the third-party system will eventually be slow, unavailable, or wrong — because at scale, it will be. That means timeouts with sensible defaults, exponential backoff on retries, dead-letter queues for messages that fail repeatedly, and alerting that tells your team about a problem before your customers do.
Tech Stack
.NET Core (C#), Node.js, Java, Python — matched to your existing stack or chosen fresh for greenfield APIs. GraphQL (Apollo/Hot Chocolate), REST with OpenAPI/Swagger, OAuth2/JWT authentication, Redis for caching and rate limiting, and N8N for low-code integration workflows where a full custom build isn't justified.
API Design Practices We Follow
The difference between an API that scales cleanly and one that becomes a support burden usually comes down to these fundamentals, applied consistently.
Versioning From Day One
Every API ships as `/v1/` from the start, so breaking changes ship as `/v2/` instead of breaking every existing integration overnight.
Consistent Error Responses
A predictable error shape (status code, machine-readable error code, human-readable message) means client apps can handle failures gracefully instead of guessing.
Pagination on Every List Endpoint
No endpoint returns an unbounded list — cursor or offset-based pagination is standard, protecting both your database and the client's memory.
Idempotency on Writes
Payment and order-creation endpoints accept an idempotency key so a retried request after a timeout never double-charges or double-creates a record.
Why V2S Infosystem
V2S Infosystem Private Limited builds and consumes APIs at scale in-house — our own recharge distribution platform runs on custom API integrations processing real transaction volume every day.
Production API Experience
We run high-throughput GET/POST APIs for our own products, not just client work — we know what breaks at scale.
Documentation Included, Not Extra
Every API ships with OpenAPI/Swagger docs as standard, not as a billable add-on you have to remember to ask for.
Security-First Design
Authentication, rate limiting, and input validation are designed in from day one, not bolted on after a security incident.
3+ Year Client Retention
Clients keep us on retainer for ongoing integration work because the first project held up under real production load.
Whether you need a single payment gateway wired up or a full API layer exposing your platform to partners, we scope the smallest engagement that solves the actual problem — not the biggest one we could bill for.
Frequently Asked Questions
Should we build a REST API or GraphQL?
REST is simpler, more widely understood, and easier to cache — the right default for most APIs, especially public ones. GraphQL wins when a mobile app or dashboard needs flexible, client-driven queries across deeply nested data and over-fetching is hurting performance. We'll recommend based on your actual client's needs, not a default preference.
How much does a custom API cost?
A simple CRUD API typically runs $15,000-$40,000. A medium REST API with 20-50 endpoints and complex business logic runs $40,000-$120,000. Enterprise API gateways with multiple partner integrations can run $150,000-$500,000. A single third-party integration on its own is much cheaper — often $290-$4,000 depending on complexity.
What third-party systems can you integrate with?
Payment gateways (Razorpay, Stripe, PayPal, UPI, BBPS), CRMs (Salesforce, HubSpot, Zoho), ERPs (SAP and custom systems), logistics/shipping carriers, marketing tools, and virtually any system that exposes a documented API or webhook.
How do you secure an API?
Every API we build includes OAuth2 or API-key authentication, rate limiting to prevent abuse, input validation to block injection attacks, HTTPS-only transport, and audit logging so you can trace exactly who called what and when.
What happens if a third-party API we depend on changes or goes down?
We build integrations with retry logic, circuit breakers, and monitoring/alerting so a downstream outage degrades gracefully instead of crashing your whole system, and your team gets notified before customers start complaining.
Do you provide API documentation for our developers?
Yes — every API ships with OpenAPI/Swagger documentation, example requests and responses, and authentication instructions, so any developer (internal or a partner's) can integrate without needing a call with us first.
Can you add an API to our existing application without rebuilding it?
In most cases, yes. We build an API layer on top of your existing database and business logic — the application itself doesn't need to be rewritten, though we'll flag anything architecturally that would make the API layer fragile long-term.
Do you offer ongoing support after the API is live?
Yes — most clients move to a monthly retainer after launch, covering monitoring, uptime response, third-party API version updates, and incremental new endpoints as their product grows. This is usually more cost-effective than a large fixed-scope project every time a new integration is needed.
Ready to Connect Your Systems?
V2S Infosystem Private Limited builds secure, documented APIs and integrations that keep your data moving automatically — no more manual re-entry, no more disconnected tools.