API development services for products and organizations

REST exposes resources at fixed addresses and returns a fixed shape; GraphQL exposes one endpoint where the caller asks for exactly the fields it needs. REST suits public and partner APIs, simple caching and broad tooling. GraphQL suits apps that read related data in many shapes or serve several client apps. Webhooks and gRPC cover event notification and internal high-volume calls. We choose per project; the comparison table above sets out when each fits.

API development builds an API: the interface that exposes your product or system to apps, partners and other software. API integration connects systems that already exist, using their APIs, so data flows between them. If you need an interface created, start here. If your CRM, accounting or ERP tools exist and need to share data, see software and API integration, or ERP integration services when the ERP is the centre. Many projects need both, and we plan them together.

Timeline Digital does not publish prices for custom software, because every project is custom. The price is set in three steps: we analyse your requirements, build a free pilot of 2 to 3 key modules, and after you approve the pilot we agree the scope, milestones and commercial terms in writing. Any change request outside the approved scope is reviewed and agreed with you before extra work begins. For an API the price follows the number of endpoints and consumers, the authentication model, the state of any system the API sits on, and the documentation, testing and monitoring you need.

There is no fixed timeframe: the schedule for your API is set from your requirements in the Plan step. The free pilot of 2 to 3 key modules is ready in about 2 days, and with 1,200+ developers we have the capacity to deliver a complete system in as little as 2 weeks. For APIs the main factors are the number of resources and consumers, how clear the existing data and business rules are, and how quickly access and approvals arrive. The full project starts after you approve the pilot, and the scope, milestones and terms are agreed after it.

Usually, yes. We build an API layer that reads and writes through the application’s own business rules where it exposes them, or through a carefully scoped database access layer where it does not, and we begin with read-only endpoints so the first consumers can be proven safely. The older system keeps running while new tools connect. If it is failing in other ways, legacy software modernization covers replacing it in stages. We tell you plainly in the Understand step if a system is a poor candidate.

You do. Project source code, the OpenAPI description, designs and documentation transfer to you on full payment, and cloud and repository accounts are set up in or moved to your name. A non-disclosure agreement (NDA) can be signed before you share sensitive details. The full terms are on our IP and ownership policy page.

Through engineering practices applied to every endpoint: OAuth 2.0 and OpenID Connect or API keys as the project needs, authorization checks per resource and action, schema validation of all input, rate limiting, encryption in transit, restricted error messages, separate environments, and logging with alerts. We test for common API weaknesses such as broken object-level authorization and excessive data exposure before go-live. These are practices, not certifications or a compliance guarantee; if your sector requires specific evidence, we agree it in the Plan step. See security and data protection.

Yes, both are part of the build. Each API has an OpenAPI description, generated reference pages with worked examples, an authentication guide and a changelog. Versioning follows a written policy: additive changes ship without breaking callers, breaking changes go into a new version, and a deprecation period is agreed so partners have time to move. Your own team or a future vendor can then work from the documentation without us.

Yes. We start with a review of the contract, code, tests, security and monitoring, and report what is sound and what is risky. From there we can document it, add tests and monitoring, fix the highest-risk issues, add a new version or run it under a support agreement. See software maintenance and support for how takeover and SLA support work.

Yes, if you want them. We build web applications and mobile apps that call the API, and the admin tools that run alongside. We can also build only the API for your own front-end or partner team. Because the contract is agreed first, the API and the apps can be built in parallel.

The choice is made per project in the Select Technology step. Common options are ASP.NET Core (.NET), Node.js with NestJS and Laravel for the service, PostgreSQL or SQL Server for data, Redis for caching, Docker for repeatable deployment and AWS or Azure for hosting. They are chosen to fit; your own stack is a valid answer if your team will maintain the API, and we will work in it. The technologies page lists the wider stack.