I build clean, documented, production-ready APIs that your team, partners, and applications can rely on. Django REST Framework and FastAPI -- designed for performance, security, and maintainability.
Every modern application needs a solid API. Whether you are building a mobile app that talks to a backend, a SaaS product with a public API for developers, or an internal system that needs to connect with third-party services -- the quality of your API determines how fast you can build, scale, and integrate.
A well-built API is more than just endpoints. It includes proper authentication, input validation, error handling, rate limiting, versioning, documentation, and monitoring. Cutting corners on any of these leads to security vulnerabilities, broken integrations, and developer frustration.
I am Kirill Strelnikov, a freelance backend developer based in Barcelona. I have built REST APIs for SaaS products, e-commerce platforms, AI chatbots, CRM integrations, and mobile applications. My APIs handle millions of requests with clean code, comprehensive docs, and production-grade reliability.
Backend APIs for web and mobile applications. User management, data CRUD, file uploads, real-time features. The backbone of your SaaS, marketplace, or internal tool.
Connect your systems with third-party services: payment gateways, CRM, messaging platforms, cloud storage. Webhook receivers, data sync, and event-driven architecture.
APIs for your customers and partners. Full documentation, API keys, usage limits, sandbox environment, and developer portal. Let others build on your platform.
Django REST Framework: My default choice for full-featured APIs. Built-in serialization, authentication, permissions, throttling, pagination, and filtering. Automatic OpenAPI schema generation. Best for APIs with complex business logic and data relationships.
FastAPI: For high-performance APIs where speed matters. Async support, automatic docs, type validation, and WebSocket support. Best for microservices, real-time applications, and AI-powered endpoints.
Security by default: Every API includes OWASP Top 10 protections: SQL injection prevention (ORM), XSS protection, CSRF tokens, rate limiting, input validation, and secure authentication. No security shortcuts.
I design the API schema first: endpoints, data models, authentication flow, error codes, and versioning strategy. You review the OpenAPI spec before development starts. Good API design prevents breaking changes later.
Test-driven development with comprehensive test coverage. Each endpoint is built with serialization, validation, permissions, and error handling. Weekly demos with Postman collection so you can test as I build.
Auto-generated Swagger/OpenAPI docs, Postman collection, and a developer guide with authentication examples, common workflows, and error handling patterns. Documentation is generated from code -- always accurate.
Load testing to verify performance under expected traffic. Security audit. Docker deployment with health checks, logging, and monitoring. Your API is production-ready with confidence.
Built a REST API for a multi-tenant SaaS platform managing shifts, overtime, and payroll for 5 cafe locations. Endpoints for employee check-in/out, schedule management, report generation, and Excel export. Role-based access control ensures managers see only their location data.
Built a complete e-commerce API: product catalog with categories, user accounts, shopping cart, wishlist, loyalty points, order management, and payment processing. Webhook integration for inventory updates and shipping notifications.
Fixed-price contracts. All prices include design, development, testing, documentation, and 30 days of post-launch support.
Kirill is a freelance backend developer in Barcelona specializing in API development, web application development, and SaaS architecture. He has built APIs for e-commerce platforms, SaaS products, AI chatbots, and CRM integrations. His APIs power applications serving thousands of users with 99.9% uptime.
Stack: Python, Django REST Framework, FastAPI, PostgreSQL, Redis, Docker. Fixed-price contracts. English, Spanish, Russian.
Tell Kirill about your project. He will design the API schema, estimate the timeline, and provide a fixed-price proposal -- within 24 hours.
Book a free API consultation