API Development & Integration Services

API development is the process of designing, building, testing, and deploying Application Programming Interfaces — software contracts that define how two systems communicate. An API specifies what requests can be made, what data formats are used, what authentication is required, and what responses will be returned. API development produces the server-side logic that fulfils those contracts — handling incoming requests, processing business logic, querying databases, and returning structured responses. APIs are the foundation of modern software: they connect mobile apps to backends, web frontends to services, SaaS products to integration partners, and systems to each other.

REST is the most widely used API style — it uses HTTP methods (GET, POST, PUT, DELETE) and returns JSON responses. It is simple, well-supported by all programming languages, and the default choice for public APIs and mobile backends. GraphQL is a query language that lets clients request exactly the data they need — useful when different consumers need different data shapes, and when over-fetching (receiving more data than needed) is a performance problem. gRPC is a high-performance binary protocol using Protocol Buffers and HTTP/2 — it is faster than REST and GraphQL but requires more tooling and is less human-readable. It is the right choice for internal microservice communication and IoT. REST is the right default; switch to GraphQL or gRPC when you have specific requirements that justify the additional complexity.

API development cost depends on the number of endpoints, business logic complexity, authentication requirements, third-party integrations, and documentation scope. A focused internal API with 10 to 20 endpoints typically ranges from USD 15,000 to USD 50,000. A mid-complexity public API with authentication, rate limiting, documentation, and a developer portal ranges from USD 40,000 to USD 120,000. A complex API platform with GraphQL, multiple consumer types, API gateway implementation, and full monitoring ranges from USD 80,000 to USD 300,000 or more. Integrating with a single third-party platform typically ranges from USD 5,000 to USD 30,000 depending on the complexity of the integration. Zenkins provides detailed proposals after an initial scoping session.

API integration is the process of connecting two or more systems by implementing the API communication between them. When you integrate your e-commerce platform with Stripe for payments, your HR system with Slack for notifications, or your CRM with your ERP for customer data sync, you are doing API integration. Integration work includes authenticating with the third-party API, mapping your data model to theirs, handling the data transformation, managing authentication token refresh, writing error handling for upstream failures, and maintaining the integration as upstream APIs evolve.

API versioning is how you introduce breaking changes without breaking existing consumers. We use URL path versioning (/api/v1/, /api/v2/) for most public APIs because it is explicit and easy for consumers to understand. For internal APIs, we prefer header-based versioning which keeps URLs clean. Our versioning strategy includes: communicating deprecation notices at least 90 days in advance, running multiple API versions simultaneously during transition periods, providing migration guides when breaking changes are unavoidable, and monitoring consumer version adoption to know when old versions can be safely retired.

API security at Zenkins is built to the OWASP API Security Top 10 standard. For all production APIs this means: HTTPS enforcement (no plain HTTP accepted), OAuth 2.0 with correctly scoped access tokens for user-facing APIs, HMAC-signed API keys for server-to-server authentication, JWT tokens with short expiry and refresh rotation, rate limiting per API key and per IP address, input validation and schema enforcement at the API boundary, no sensitive data in URLs (query parameters are logged by default), secrets stored in vault (never in code or environment files), and pre-launch security scanning with OWASP ZAP. For regulated industries, we additionally implement FAPI (Financial-grade API Security Profile) for fintech and HIPAA-aligned access logging for healthcare.

An API gateway is a reverse proxy that sits in front of your APIs and handles cross-cutting concerns — authentication verification, rate limiting, request routing, response caching, SSL termination, and API analytics. Rather than implementing these in every individual API, the gateway handles them centrally. You should use an API gateway if: your APIs are consumed by external developers or partners, you have multiple backend APIs that need a unified entry point, you need fine-grained rate limiting per consumer, or you need API analytics without instrumenting each service. Popular options include Kong (open-source, self-hosted), AWS API Gateway (managed, usage-based pricing), and Azure API Management. Zenkins recommends and implements the appropriate gateway for your architecture.

We write API documentation using the OpenAPI 3.x specification, which generates interactive documentation via Swagger UI or Redoc. The documentation includes: every endpoint with its full request schema, response schema, and example payloads; authentication instructions with step-by-step OAuth flow diagrams; working code examples in cURL, Python, JavaScript, and PHP; error code reference explaining what each error means and how to resolve it; rate limit documentation with guidance on handling 429 responses; a versioning and changelog section communicating upcoming breaking changes; and SDK generation using OpenAPI Generator for clients who prefer a typed library. For event-driven APIs, we produce AsyncAPI documentation covering event schemas, broker configuration, and consumer group setup.

Yes. APIs require ongoing maintenance because the systems they integrate with evolve. Third-party platforms deprecate API versions, introduce new authentication requirements, change rate limit policies, and update webhook payload schemas. Our post-launch API support covers: upstream API version upgrade management, security patch application (authentication library updates, dependency vulnerability fixes), monitoring alert response, performance optimisation as consumer volume grows, and documentation updates when API behaviour changes. We offer monthly retainer or annual support contracts. Many clients retain Zenkins specifically for integration maintenance because the institutional knowledge of what each integration does and why is difficult and costly to hand off.

Yes. Zenkins has delivered integrations with SAP (S/4HANA and SAP ECC using OData APIs, RFC/BAPI, and IDocs), Salesforce (REST and SOAP APIs, Bulk API for large datasets, Salesforce Connect for external object access, and Change Data Capture for real-time sync), Microsoft Dynamics 365 (Dataverse API, Power Automate connectors), Oracle NetSuite (REST and SuiteTalk SOAP APIs), Workday (REST and SOAP APIs for HRIS integration), and ServiceNow (REST API for ITSM data exchange). Enterprise system integrations require careful attention to data model mapping, bulk data handling, authentication token management, and error handling for the specific quirks of each platform.