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5.0 on Clutch OpenAI Select Partner

Custom Software Development

Custom API Development Company

APIs are how your apps, systems and partners talk to each other. We design and build custom REST and GraphQL APIs, and integrate third-party ones, so data moves securely between your mobile apps, web platforms, ERP, CRM and payment providers.

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What
Custom API Development Company, run by Creuto.
Where
Clients in the US, UK, Australia, UAE, Vietnam and India, with calls planned around your working day.
Recognition
OpenAI Select Partner, 5.0 on Clutch from 16 verified reviews, 120+ products shipped.
Who leads it
Founder and CEO Nihar Ranjan Rout: 8+ years in product, 120+ products shipped.
How it starts
A free 30-minute call, a written proposal within 24 hours, a PRD, then a first working version in about 4 weeks.

What our API development services cover

  • Custom REST and GraphQL APIs

    Well-designed APIs for your mobile apps, web apps and partners, with clear documentation.

  • Third-party API integration

    Payments, maps, messaging, accounting, logistics and AI services connected to your product.

  • ERP and CRM integration

    Orders, customers, stock and invoices kept in sync between your systems.

  • Public and partner APIs

    APIs that customers and partners can build on, with keys, limits and versioning.

  • API modernisation

    Old or fragile APIs rebuilt, documented and made faster without breaking existing apps.

Key features we build into API development projects

  • OpenAPI documentation

    Clear, versioned documentation with examples for every endpoint.

  • Authentication and access

    OAuth 2.0, API keys, scopes and role-based permissions.

  • Rate limiting and quotas

    Protection from abuse and fair use for partners.

  • Webhooks and events

    Real-time notifications to other systems when something changes.

  • Monitoring and logs

    Response times, errors and usage tracked so issues are caught early.

  • Backward-compatible versioning

    New features without breaking apps that already use the API.

How we approach API Development

We start from the clients that will use the API: your apps, internal systems and partners, and the data each one needs. We agree the contract first in an OpenAPI or GraphQL schema, then build with authentication, validation, rate limits and logging from the start, test against real integrations and publish documentation before anyone depends on it. Versioning means existing apps keep working when the API grows.

When this is a good fit

A good fit when

  • Your systems do not talk to each other and data is copied by hand.
  • Your mobile or web app needs a reliable back end.
  • Partners or customers want to connect to your platform.

Why choose Creuto for API development

  • Founder-led from day one

    You speak with Nihar Ranjan Rout, who scopes and leads your API development project, not a sales team.

  • A written plan before code

    A proposal within 24 hours of the first call, then a PRD that fixes scope, priorities and milestones.

  • Working software early

    A first working version in about 4 weeks, then improvements in milestones you can see and test.

  • Recognised by clients

    OpenAI Select Partner and rated 5.0 on Clutch from 16 verified reviews, with 120+ products shipped.

How an engagement works

  1. 01

    Scope

    A free strategy call, then a clear proposal with scope and priorities.

  2. 02

    Plan

    A PRD and, where useful, a clickable prototype before building starts.

  3. 03

    Build

    An in-house team builds in stages, with demos along the way.

  4. 04

    Launch and improve

    Release, then keep improving with the people who built it.

Technology we use for API development

  • Node.js
  • Python
  • Java
  • GraphQL
  • PostgreSQL
  • Redis
  • Docker
  • AWS
  • Azure

See the full technology stack

Products we have built

How we keep quality and security high

  • Code review on every change

    A second engineer reviews code before it is merged.

  • Testing before each release

    Key flows tested on real devices and browsers, with automated checks where they pay off.

  • Security basics built in

    Access control, encrypted connections and secrets kept out of code from the first sprint.

  • Staged releases

    Changes go to a staging environment for your review before they reach users.

  • Documentation

    Setup notes and decisions written down, so your team or any future team can maintain the product.

  • Support after launch

    A 60-day warranty after launch, then an agreed plan for maintenance and new work.

API Development for companies worldwide

We build API development for startups and enterprises in these cities, with calls planned around their working day:

More in Custom Software Development

Industries we build this for

Questions about API Development

Are you a custom API development company?

Yes. Creuto is a founder-led software, mobile app and AI development company with its delivery team in India. We provide API development services for startups and enterprises in the US, UK, Australia, the UAE and India, and you work with Nihar Ranjan Rout directly, starting with a free 30-minute call.

REST or GraphQL?

REST is simple and widely supported, and suits most integrations. GraphQL suits apps that need flexible queries across many related objects. We recommend one based on your clients and data, and explain why.

How do you secure APIs?

With authentication such as OAuth 2.0 or API keys, role-based access, encryption in transit, input validation, rate limiting and logging of sensitive actions.

Will you document the API?

Yes. We provide OpenAPI documentation and examples, so your team and partners can integrate without guesswork.

How much do API development services cost?

It depends on scope, platforms and integrations. Use the free app timeline calculator to see how long it takes, or book a call and get a written proposal within 24 hours.

Can you integrate payment gateways and UPI?

Yes. We integrate payment gateways, UPI, cards and wallets, including webhooks for payment status and refunds.

Can you connect our ERP or Tally to other systems?

Yes. We build integration layers that sync orders, invoices, stock and customers between your ERP or accounting software and other tools.

How long does an API project take?

A focused API or integration can be working in a few weeks. Larger platforms with many integrations take longer, and the written proposal sets out the milestones.

Do you sign an NDA before we share our idea?

Yes. We sign an NDA before discovery, so you can share your idea, data and plans openly.

What happens after the API development project launches?

There is a 60-day warranty after launch for fixes. After that we agree a support plan covering updates, monitoring and new features.

Do you work with clients in other countries?

Yes. We work with clients in the US, UK, Australia, the UAE, Vietnam and India, with calls planned around your working day.

Guides on this topic

Who you’ll work with: Nihar Ranjan RoutFounder & CEO of Creuto. 8+ years in product, 120+ products shipped. Read the story

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