APIs that connect everything and stay secure

What does an API development company build?

An API development company builds the interfaces that let software talk to other software: the backend your mobile app calls, the endpoints partners use to send you orders, and the webhooks that tell other systems when something happens. Varsuite designs, builds, documents and looks after those APIs so they are secure, predictable and easy to integrate with.

Typical API projects include:

• Backends for mobile apps, including login, data sync and push notifications
• Partner and customer APIs so other businesses can integrate with your platform
• Integration APIs that connect your CRM, accounts, stock or booking systems
• Webhooks that notify other systems the moment orders, payments or bookings change
• Public or private APIs for a SaaS product

If you mainly need to connect existing tools rather than expose your own API, our data integrations service may be the better starting point.

What is the difference between a REST API and a webhook?

A REST API waits to be asked: another system sends a request and gets a response. A webhook works the other way round: your system sends a message to another system the moment something happens. Most good integrations use both.

How they compare:

• REST API. The client pulls data when it needs it, for example a mobile app loading a customer's orders. Predictable, easy to cache and easy to test, but the client has to keep asking if it wants to spot changes.
• Webhooks. Your platform pushes an event, such as order.paid, to a URL the partner provides. Near real time and efficient, but the receiver must be online, and delivery needs retries, signatures and logging to be dependable.

We build webhooks with signed payloads, automatic retries with backoff, a delivery log and a way to replay failed events, so a partner outage does not mean lost data. Where it genuinely suits the job we also consider GraphQL or real-time streams, but REST with webhooks covers most business needs well.

How do you secure an API?

We secure APIs with strong authentication, permission checks on every endpoint, rate limiting, input validation and logging, then test them the way an attacker would. Every API quote includes a penetration test and a security code review before launch.

The controls we build in:

• Authentication using API keys, OAuth 2.0 or signed tokens, depending on who is calling
• Authorisation checked on every request, so one customer can never read another's data
• Rate limiting per key or user, to protect the service from abuse and runaway scripts
• Validation of every input, with clear error messages that do not leak internals
• Audit logs and monitoring, so unusual activity is spotted and can be traced
• HTTPS everywhere, with secrets stored encrypted and keys that can be rotated

For protection after launch, our security monitoring service watches for threats and new vulnerabilities.

How do you document and version an API?

We document every API with an OpenAPI specification and readable reference pages, and we version it from the first release so changes never break the apps and partners that depend on it. Good documentation makes an API quick to integrate with, and good versioning keeps it trustworthy.

In practice that means:

• An OpenAPI (Swagger) specification kept in step with the code, so the docs match what the API really does
• Example requests and responses for every endpoint, plus a sandbox to try them
• A version in the URL or header, such as /v1, with breaking changes only in a new version
• A published deprecation policy and changelog, so partners get notice before anything is retired
• Automated contract tests that fail the build if a change would break existing clients

Can we try the API before we commit?

Yes. We build you a free working demo first: a live sandbox API with real endpoints, sample data and documentation, so your developers or partners can call it before you commit to anything. Going from that sandbox to a production API costs less than most people expect.

The demo usually covers the part that matters most, such as a partner placing an order or a mobile app loading an account, with a webhook firing back. If it proves the approach, we agree a fixed quote before any paid work starts. Our pricing page explains how quotes work.

How are your APIs built, tested and looked after?

AI agents do the heavy lifting on the build, and a UK human team based in Lancashire reviews, perfects and signs off every release. Automated tests run from day one, covering each endpoint, permission rule and webhook, so the API proves it still works every time it changes.

After launch, ongoing monthly care covers updates, dependency and security patches, monitoring, and new endpoints as your partners' needs grow. We can add load testing and deeper checks through our testing and QA service. You own the API and its code, and we are happy to hand over access and explain how everything works.