API development and integration services in India

We design secure, well-documented APIs and connect the systems your business runs on, so CRM, ERP, payments, website and apps share data automatically instead of by hand.

  • Free strategy call
  • Custom quotation, never a fixed package
api/routes/orders.ts
1// Validated, authenticated, documented2app.post('/v1/orders', requireApiKey, async (c) => {3  const input = OrderSchema.parse(await c.req.json());4  const order = await orders.create(input);5  await webhooks.emit('order.created', order);6  return c.json(order, 201);7});
  • REST and GraphQL
  • Validation
  • Webhooks
  • OpenAPI docs

Worked with

Problems we solve

Are your systems copying data by hand instead of talking to each other?

Most businesses run on several systems: a website, CRM, accounting, payments, an app. When they aren't connected, people become the integration.

  1. 01

    Data typed twice

    Orders, leads and invoices are re-entered between systems, and errors creep in.

  2. 02

    Fragile integrations

    Old scripts and plugins break silently, and nobody notices until data is missing.

  3. 03

    No API for partners

    Partners and customers want to connect to your system, but there's no secure, documented API.

  4. 04

    Slow or insecure APIs

    Existing APIs are slow, undocumented or expose more data than they should.

Our solution

Clean APIs and integrations that fail loudly, not silently

We design APIs and integrations as products: secure, documented, monitored and easy to change.

  • Design first

    Endpoints, data contracts, authentication and error handling designed and documented before code is written.

  • Secure by default

    Authentication, input validation, rate limits and least-privilege access on every endpoint.

  • Monitored and recoverable

    Retries, idempotency, logs and alerts, so failed syncs are caught and fixed, not lost.

API services

What we build

API development and integration services for websites, apps, SaaS products and business systems.

01

Custom API development

REST and GraphQL APIs for your web and mobile apps, partners and internal systems, with validation, authentication, versioning and documentation.

  • REST and GraphQL APIs
  • Authentication and API keys
  • Input validation
  • Versioning
  • Rate limiting
  • OpenAPI documentation
02

Third-party API integration

Connect your systems to the services you use: payment gateways, messaging, email, maps, shipping, accounting and SaaS tools.

  • Payment gateways
  • WhatsApp Business API
  • Email and SMS
  • Shipping and logistics
  • Maps and location
  • SaaS tools
03

CRM, ERP and accounting integration

Synchronise customers, orders, stock, invoices and payments between your CRM, ERP, accounting software and website.

  • Customer and lead sync
  • Order and stock sync
  • Invoice and payment sync
  • Scheduled and real-time sync
  • Conflict handling
  • Sync dashboards
04

Webhooks and event-driven integration

Real-time events between systems with webhooks and background jobs, including retries and idempotency so nothing is processed twice.

  • Incoming and outgoing webhooks
  • Background jobs
  • Retries and back-off
  • Idempotency
  • Event logs
  • Failure alerts
05

Partner and public APIs

Secure APIs for partners and customers to integrate with your platform, with keys, scopes, usage limits and developer documentation.

  • API keys and scopes
  • Usage limits
  • Developer documentation
  • Sandbox environment
  • Change notices
  • Usage analytics
06

API audit and modernisation

Review existing APIs and integrations for security, performance and reliability, then fix or rebuild them without breaking clients.

  • Security review
  • Performance profiling
  • Error handling
  • Documentation
  • Versioned migration
  • Monitoring

What you get

What connected systems change

Integration is worth doing when it removes manual work and errors.

  • No double entry

    Data flows between systems automatically.

  • One version of the truth

    Every system shows the same data.

  • Secure access

    Authenticated, validated, least-privilege APIs.

  • Visible failures

    Logs and alerts when something goes wrong.

  • Documented

    Clear docs for your team and partners.

  • Yours to own

    Code, keys and accounts in your name.

Why us

Why teams choose Zero One Creation

  • Integrations in our products

    Our products integrate payments, authentication and cloud storage in production.

  • Both sides of the API

    We build the apps, CRMs and ERPs that APIs connect.

  • Security-minded

    Validation, rate limits and least privilege by default.

  • Clear written scope

    A proposal with scope and a customised quotation.

List the systems you use and where data is copied by hand. We'll show you how to connect them.

A free strategy call, then a written proposal with a customised quotation.

Our approach

How we build APIs and integrations

Open each step to see what it covers.

  1. 01.Systems map

    Every system, the data it owns and where data is copied today.

  2. 02.Contracts

    Endpoints, data formats, sync rules and error handling, documented and agreed.

  3. 03.Build

    APIs and integrations built with validation, auth and tests.

  4. 04.Test with real data

    Sandbox and staged testing with real-world cases and failures.

  5. 05.Launch with monitoring

    Logs, alerts and dashboards for every integration.

  6. 06.Maintain

    Updates when third-party APIs change, and new integrations as you grow.

Common integration problems

Integration problems we fix

These are common problems in existing APIs and integrations, and how we fix them.

  • Silent failures

    What you notice
    A sync stops working and nobody notices for days.
    How we fix it
    Logging, alerts and a sync dashboard.
  • Duplicate records

    What you notice
    Retries create the same order or lead twice.
    How we fix it
    Idempotency keys and de-duplication.
  • Slow endpoints

    What you notice
    API calls time out under load.
    How we fix it
    Query optimisation, pagination and caching.
  • Over-exposed data

    What you notice
    APIs return more data than the client needs.
    How we fix it
    Scoped responses and access checks.
  • Breaking changes

    What you notice
    An API change breaks apps and partners.
    How we fix it
    Versioning and change management.
  • No documentation

    What you notice
    Only one developer knows how the API works.
    How we fix it
    OpenAPI documentation and examples.

Technology

Our API tech stack

Tools from our own products and client work, chosen per project.

API frameworks
Node.jsHonoExpressDjango REST
Contracts
RESTGraphQLOpenAPIZod validation
Auth
API keysOAuthBetter AuthJWT
Data
PostgreSQLMongoDBDrizzle ORM
Async
WebhooksBackground jobsInngestQueues
Integrations
RazorpayStripeWhatsApp Business APIEmail servicesS3

Options

Custom integration, integration platform or manual work?

How the main options compare.

Custom integration, integration platform or manual work?
CriteriaCustom integrationIntegration platform (no-code)Manual export and import
Fit with your systemsBuilt for exactly what you usePre-built connectorsAny system, by hand
Complex logicFully supportedLimitedDepends on people
ReliabilityRetries, logs and alertsPlatform monitoringError-prone
Running costBuild plus hostingSubscription by usageStaff time
Best forCore business data flowsSimple, standard connectionsRare, one-off transfers

Integration platforms are great for simple flows. We use them where they fit and build custom where they don't.

Use cases

Integrations across industries

Common integrations we build.

  • Manufacturing

    Portal, ERP and accounting kept in sync.

    See the work
  • Education

    Admissions, LMS, payments and messaging connected.

    See the work
  • E-commerce

    Store, inventory, shipping and accounting sync.

    See the work
  • SaaS products

    Public APIs, webhooks and partner integrations.

    See the work
  • Sales teams

    Website forms and WhatsApp into the CRM.

    See the work
  • AI agents

    Secure tools that let agents act in your systems.

    See the work

How we work together

Three ways to work with us

Every engagement starts with a written proposal and a customised quotation.

  • Integration project

    Design and build of agreed APIs or integrations.

    Best for: Connecting specific systems

  • API audit

    A review of existing APIs and integrations with a fix plan.

    Best for: Unreliable or insecure integrations

  • Ongoing support

    Monitoring, updates and new integrations.

    Best for: Businesses with many connected systems

Guide

API development and integration: a practical guide

What is an API?

An API (application programming interface) is a defined way for one piece of software to request data or actions from another. Your mobile app, website, CRM and payment gateway all talk to each other through APIs.

A well-designed API has clear endpoints, predictable data formats, authentication, error messages and documentation.

REST or GraphQL?

REST APIs expose resources at fixed URLs and are simple, widely supported and easy to cache. GraphQL lets clients ask for exactly the data they need in one request, which suits complex front ends.

Most business integrations use REST; GraphQL is useful for products with many different screens and clients.

Making integrations reliable

Networks fail and third-party services go down. Reliable integrations retry with back-off, use idempotency so retries don't create duplicates, log every attempt and alert someone when failures continue.

A simple dashboard showing the status of each sync saves hours of investigation.

API security basics

Authenticate every request, validate every input, return only the data the client needs, apply rate limits and keep secrets out of client apps and code repositories.

Rotate keys regularly and give each integration only the permissions it needs.

Common integrations for Indian businesses

The integrations we see most often connect a website or app to a CRM, a CRM to accounting software, an order system to an ERP, payments through a payment gateway, and messages through SMS, email and the WhatsApp Business Platform.

Each one removes a manual step, such as re-typing an enquiry, copying an order into accounts or sending a payment reminder by hand. The best place to start is usually the step your team repeats most often.

Documentation and versioning

An API is only as useful as its documentation. Clear documentation lists every endpoint, its inputs and outputs, error codes and examples, so your team or partners can use it without guessing.

Versioning lets you improve an API without breaking the systems that already use it. Changes that would break existing users go into a new version, and old versions are retired with notice.

Testing and monitoring integrations

Integrations fail in ways ordinary pages don't: a third-party service is slow, returns an unexpected format or changes without warning. Automated tests, test environments and sample data catch many problems before they reach production.

Once live, monitoring should alert your team when calls fail or queues build up, with logs that show exactly which record failed and why.

Taking over an existing integration

Many businesses come to us with integrations built by someone else that fail silently or need constant fixing. The first step is an audit: what connects to what, where data is lost, and which parts are undocumented.

From there, we usually stabilise the most important flows first, add logging and alerts, and then decide whether to improve or rebuild the rest.

Webhooks and real-time updates

Many services can notify your system the moment something happens, such as a payment succeeding, a form being submitted or an order being shipped. These notifications, called webhooks, are faster and lighter than checking for changes repeatedly.

Webhook handlers should verify that the message is genuine, handle duplicates safely and record what they received, so nothing is lost or processed twice.

What affects the cost of API development

Costs depend on the number of systems and endpoints, data complexity, real-time versus scheduled sync, the quality of third-party APIs, security needs, documentation and ongoing maintenance.

We don't publish fixed prices or packages. After a strategy call, we send a written proposal with a customised quotation.

Before you talk to us

Frequently asked questions

What are API development services?

Designing and building APIs that let your software share data and actions, plus integrating your systems with third-party services through their APIs.

Can you integrate our CRM with our website and accounting?

Yes. Leads from the website can flow into the CRM, and orders, invoices and payments can sync with accounting software through its integration options.

Can you integrate the WhatsApp Business API?

Yes. We integrate WhatsApp for messages, templates and lead capture, connected to your CRM or support tools.

Do you build public APIs for partners?

Yes, with API keys, scopes, usage limits, sandbox environments and developer documentation.

How do you keep APIs secure?

With authentication, input validation, least-privilege access, rate limits, secret management and monitoring.

What happens when a third-party API changes?

We monitor integrations and update them when providers change their APIs, as part of ongoing support.

Can you fix our unreliable integrations?

Yes. We audit them, add retries, idempotency, logging and alerts, and fix or rebuild what's broken.

Do you provide API documentation?

Yes. We document endpoints, inputs, outputs, errors and examples, and keep the documentation updated as the API changes.

Can you integrate payment gateways?

Yes, including payment links, webhooks for payment status and reconciliation with your order or accounting system.

Can integrations run in the background?

Yes. Long or bulk tasks run in background queues with retries, so users aren't kept waiting.

How much does API development cost in India?

It depends on systems, endpoints, sync needs, security and maintenance. We do not publish fixed prices; share your requirements and we will send a customised quotation.

Contact us

Tell us which systems need to talk to each other.

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