Most of our work connects platforms that already have an API. Sometimes the API you need does not exist yet — the system is bespoke, built in-house, or was never designed to be spoken to from outside. In those cases we design and build the API itself: a documented, versioned, monitored interface that sits in front of your system and gives every other tool a safe, predictable way in.
When a custom API is the right call
- An in-house or legacy application holds data other systems need, but exposes nothing beyond its own screens.
- You want to give customers or trading partners controlled access to your data without opening the underlying database.
- A new mobile app, customer portal or storefront needs a stable back-end that will not change every time the core system does.
- Several internal systems need to be consolidated behind one consistent interface rather than integrated pair by pair.
- An existing API is undocumented, unversioned or unsafe to call directly, and needs a controlled layer in front of it.
What we build
- REST or GraphQL endpoints modelled around your business objects, not your database tables.
- Authentication and authorisation — OAuth 2.0, API keys, signed requests or mutual TLS, with per-client scopes and quotas.
- Versioning and deprecation built in from day one, so future changes never break the clients already using it.
- Rate limiting, queuing and idempotency so a burst of traffic or a repeated call cannot overload or corrupt the system behind it.
- Webhooks and event streams for the cases where clients need to be told about a change rather than poll for it.
- An OpenAPI specification, reference documentation and a sandbox environment, plus a client library where it saves your integrators time.
- Logging and metrics on every request, so any individual call can be traced end to end.
How we work
- Contract first. We agree the endpoints, payloads and error behaviour as a written specification before any code is written, and review it with the teams that will consume it.
- Fixed scope, fixed price. The build is quoted against that specification. You know the cost before we start.
- Built against a sandbox that mirrors production, then acceptance tested with your own data.
- Handed over in full — source code, infrastructure definition, credentials and documentation. There is no licence fee for continuing to run it, and any competent developer can maintain it.
Bespoke API support & SLAs
A custom API becomes part of your operational infrastructure, and other systems come to depend on it. Once it is live we offer a support agreement that covers monitoring, incident response, and the ongoing work of keeping the interface stable as the system behind it changes.
What a support agreement covers
- Uptime and health monitoring of every endpoint, with alerting the moment error rates or latency move outside their normal range.
- Incident response to agreed targets — see the tiers below — including diagnosis, a fix or rollback, and a written explanation of what happened.
- Version and deprecation management — new versions shipped alongside old ones, consumers given notice, and old versions retired only once nothing is using them.
- Dependency tracking. When the underlying system is patched or upgraded, we review the API against it ahead of the change rather than after it breaks.
- A pool of included change requests each period for small additions and adjustments, so minor needs do not each become a separate quote.
- A named point of contact and a single place to raise issues, with everything logged.
Support tiers
| Standard | Priority | Critical | |
|---|---|---|---|
| Cover hours | Business hours, Mon–Fri | Extended hours, Mon–Sat | 24 / 7 |
| Monitoring & alerting | Endpoint health, daily digest | Real-time, on-call alerting | Real-time, on-call alerting |
| Response — service down | Next business day | 4 business hours | 1 hour |
| Response — degraded / partial | 2 business days | 1 business day | 4 hours |
| Response — question or minor issue | 3 business days | 2 business days | 1 business day |
| Target fix or workaround — service down | 3 business days | 1 business day | 8 hours |
| Included change requests | Up to 2 hours / month | Up to 1 day / month | Up to 2 days / month |
| API version migrations | Quoted per change | Included | Included |
| Quarterly review | — | Yes | Yes |
Response time is measured from when an issue is raised through the agreed channel. Targets assume we retain access to a representative environment and to the system the API fronts. Tiers and thresholds are set per engagement — the table above is our usual starting point.
Talk to us about a custom API
Tell us about the system that needs an interface and who needs to talk to it. We will come back with an outline design, a fixed build price and the support option that fits. Get in touch or call 01303 883111.