Development · Service
API Development & Integration Services for Scalable Digital Systems
Scalable API development services. We build custom APIs and connect systems to automate workflows, streamline data, and power digital transformation.
Overview
Modern businesses rely on well-connected systems — and APIs are the glue that holds them together. At A2Z, we specialise in building and integrating APIs that allow your software, apps, and platforms to communicate seamlessly.
From custom-built APIs to integrations with platforms like Stripe, Salesforce, or Xero, we develop robust solutions that simplify operations and improve efficiency. Whether you’re looking to connect a website to a CRM, integrate with third-party services, or build a secure backend API from scratch, we help you do it securely and at scale.
Our team ensures that every API we develop is reliable, scalable, and fully documented to support your ongoing growth and development.
Capabilities
What we typically cover.
- 01
Custom API Development
Design and build RESTful or GraphQL APIs tailored to your business requirements and systems.
- 02
Third-Party API Integration
Seamlessly connect to external services like Stripe, SendGrid, Twilio, HubSpot, and more.
- 03
Internal Systems Integration
Connect legacy systems, ERPs, CRMs, or databases with new digital tools for better performance and data flow.
- 04
Secure Authentication & Access Control
Implement secure token-based access and user authentication via OAuth, JWT, or API keys.
The process
Our API projects start with a discovery phase to map out data structures and integration requirements. From there, we develop clean, efficient, and well-documented APIs — tested thoroughly for performance and security. Whether standalone or part of a larger system, the result is a robust, future-proof integration that reduces manual tasks, enhances user experience, and scales as your business grows.
FAQs
What prospects usually ask.
REST or GraphQL — when does each make sense?
REST is the right default for most APIs — simpler tooling, easier caching, lower onboarding cost for the developers who consume it. GraphQL is worth the extra complexity when consumers need precise control over what fields they fetch (typically mobile apps over slow networks, or when one API serves many different UI surfaces). For most internal and partner integrations, REST is the pragmatic choice.How do you secure the APIs you build?
Layer by layer. TLS for transport, OAuth 2.0 or JWT for authentication (or signed API keys for machine-to-machine), explicit per-endpoint authorisation rules so credentials don't grant blanket access, rate limiting and abuse protection, structured logging for audit, and input validation at every boundary. For sensitive industries we add IP allow-listing and mTLS where the consumers can support it.How much does it cost to build a custom API?
A focused API for one domain (e.g. exposing inventory, customers, or bookings) typically costs £8,000–£30,000 depending on data complexity, auth requirements, and integration count. A full backend API for a SaaS or platform is more like £40,000–£150,000 over the build. Ongoing hosting and operations sit on top — usually £100–£800 a month.Can you integrate our existing systems without rebuilding them?
Yes — that's most of what API integration work is. We expose existing systems through clean, modern APIs without touching the underlying platform: a façade layer that translates between modern callers and a legacy backend, often via mirrored databases or middleware. The legacy system stays as-is; new services can finally talk to it cleanly.How do you handle versioning when APIs change?
We version explicitly from day one — typically URL-based (e.g. /v1/) for clarity. Breaking changes go to a new major version; consumers run on the old version until they migrate, with a published deprecation timeline. Non-breaking additions (new fields, new endpoints) ship under the same version. The aim is that consumer integrations never break unexpectedly.Are the APIs documented for our developers and partners?
Yes. Every API ships with OpenAPI / Swagger documentation generated from the code itself, plus a hosted developer portal with examples, error codes, and authentication walkthroughs. For partner-facing APIs we also include a sandbox environment with test credentials so external developers can experiment without touching production.Where are the APIs hosted, and how do you handle scale?
Most APIs we build run on Vercel, Cloudflare Workers, or AWS Lambda — serverless infrastructure that scales horizontally without operator intervention. Predictable workloads (e.g. internal APIs with steady traffic) can also run on traditional cloud VMs or containers if that's cheaper. Hosting choice falls out of the expected traffic profile rather than ideology.
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Where this lands most often.
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Got a system worth building? Let's talk it through.
Tell us what you're trying to solve. We'll come back inside two working days with honest thoughts on scope, approach, and what a working partnership could look like.
- hello@a2ztech.co.uk
- Studio
- Engine Shed, Bristol
- Response
- Within 2 working days
- Building since
- 2003