API development and system integration for CRMs, ERPs, payments and internal tools

An API is the interface a system exposes so other software can read its data or trigger actions, while an integration is the working connection that uses one or more APIs to keep specific systems in step. Building an API is about designing a stable, secure contract. Building an integration is about mapping data, handling failures, reconciling records and monitoring the flow over time.

Use REST when a client needs an immediate answer, webhooks when another platform must tell you something happened, and a message queue such as Kafka or RabbitMQ when several systems need the same events or work must survive an outage. Most integration architectures combine all three. We choose per data flow, based on latency, volume, ordering requirements and what each vendor supports.

They share data through published contracts and events, never by reading each other's databases. Each service owns its data and exposes it through a versioned API, or publishes events to Kafka or RabbitMQ that other services consume and store in the shape they need. Synchronous calls are kept for requests that need an immediate answer, and consumer contract tests in CI catch breaking changes before a service is deployed.

We treat every webhook as something that may arrive twice, late or out of order. Receivers verify the signature, store the event with its unique ID, acknowledge quickly and process it asynchronously, skipping IDs already handled. A scheduled reconciliation job then compares our records with the provider's API to catch anything missed, and events that fail processing go to a dead-letter queue for replay.

We use OAuth 2.0 and OpenID Connect for delegated access, issue short-lived tokens with narrow scopes, and keep client secrets and keys in a managed secrets store with rotation. Every request is authenticated and authorised at the gateway and again in the service. We add rate limiting, input validation, audit logging and alerts on unusual patterns, and expose no more personal data than each consumer needs.

Usually, yes, through a route chosen for that particular system. We can read from a read-only database replica or capture changes from its transaction log, pick up scheduled file exports over SFTP, parse structured report emails, or check whether the vendor sells an API module you have not licensed. The chosen route is then wrapped in a small adapter with a clean API. Scripting the user interface is a last resort, because it breaks whenever screens change.

They queue work and catch up when the service recovers. Outbound calls use timeouts, retries with exponential backoff and circuit breakers, and messages wait in a durable queue rather than being dropped. Once the partner is available again, the backlog processes in order. Alerts tell your team when a backlog is building, and dashboards show which partner is failing, so problems are diagnosed from evidence rather than customer complaints.

You need one once several services or external consumers share your APIs, and often not before. A gateway puts authentication, rate limits, request logging and routing in one place, so each service does not reimplement them. For a single application with one API, the same controls can live in the application and a reverse proxy such as Nginx. As partners, mobile apps and further services are added, we introduce a managed or self-hosted gateway so policies stay consistent.

Cost depends on the number of systems, the quality of their APIs, data volumes, transformation logic and security requirements. Connecting two well-documented platforms is far smaller than building a partner API with OAuth, versioning and reference documentation. After discovery we give a fixed quote per integration or phase, plus expected hosting and messaging costs, so you can start with the flows that remove the most manual work.

Timelines depend mainly on the systems involved: sandbox availability, documentation quality, data clean-up and how quickly vendors grant access. A single integration between two platforms with good APIs is often delivered within a few weeks of discovery. Multi-system programmes are phased, with each integration running alongside the old process until records reconcile, and only then does the flow switch over.

Yes. Every API we build has an OpenAPI specification kept in the repository and published as browsable reference documentation, with example requests, error codes, authentication steps and rate limits. We also write integration guides for partners, a changelog for each version and runbooks for your operations team, so the API can be maintained and extended without depending on us.

We make additive changes by default, so new fields and endpoints do not affect current clients. When a breaking change is unavoidable, we publish a new version alongside the old one, document the differences, notify consumers and agree a deprecation period with you. Usage metrics show who still calls the old version, so it is retired only after traffic has moved across.