SQL & API Integration

Build the data bridge between your systems. I develop REST and GraphQL APIs, integrate your databases, design ETL processes and ensure data flow between different platforms. I build OpenID Connect based identity infrastructure providing single sign-on across multiple applications, web service integrations between ERP and production and operations systems, and structures bringing desktop and web applications onto the same integration layer. I work with databases such as SQL Server, Oracle PL/SQL, MongoDB and Redis, and deliver APIs that are documented, versioned and secure. As a freelance software developer in İzmir, Türkiye, I work online with businesses in İzmir and the surrounding region, with regular interim deliveries so you can see what is ready at every stage.

Features

  • REST API design and development
  • GraphQL API development
  • Database integration
  • ETL process design
  • Webhook and event-driven architecture
  • API documentation (Swagger/OpenAPI)

Use Cases

  • E-commerce ERP integration
  • Bank API integration
  • Stock data synchronization
  • Third-party service connections

Who is it for?

  • Businesses with disconnected software systems
  • Teams entering the same data into several systems by hand
  • Companies that need an API for a mobile or web application
  • Organizations that want to modernize legacy systems step by step

How I work

  1. 1Discovery: I map the systems and the data flows between them
  2. 2Design: I document the data model and the API contract
  3. 3Development and testing: I validate the integration with realistic data in a test environment
  4. 4Release and monitoring: I go live in a controlled way and set up error alerts
  5. 5Maintenance: I keep the integration current as systems change

Technologies Used

  • Node.js
  • Express
  • PostgreSQL
  • GraphQL
  • Prisma
  • Swagger

Related Projects

Sample application

Single Sign-On (SSO) Infrastructure

A sample single sign-on (SSO) infrastructure built on OpenID Connect: one account for multiple applications, secure authorization with PKCE and users and permissions managed from one place.

Sample application

ERP Integration Layer

A sample web service based integration layer between an ERP and production and operations systems: automatic data exchange that removes the need to enter the same data into several systems by hand.

Sample application

Desktop Warehouse App and Web Dashboard

A sample solution made up of a C# WinForms desktop application for warehouse operations, an ASP.NET MVC web dashboard for management and a Web Service based integration layer for data exchange between systems.

Sample application

Automated Notification and Reporting Services

Sample .NET Worker Service based services that automatically deliver expiry date alerts, raw material requirement plans, temperature-humidity alarms and control reports via email, WhatsApp and SMS.

Frequently asked questions

Will it integrate with my existing system?

Most likely, yes. If your system offers an API, a web service (SOAP/REST), database access or file transfer, an integration can be built. I can connect many different systems, including ERP, identity management and industrial devices. I give you a definite answer in a free initial meeting where I review your systems.

Should I use REST or GraphQL?

For most enterprise integrations REST is sufficient and the most common choice, with broad tooling support and easy caching. GraphQL helps in rich interfaces where different screens need different parts of the same data. I make the choice with you based on who will consume the API and how your data is structured, and I can use both where it makes sense.

Can data from my old database be moved to the new system?

Yes. For data migration I first analyze the old structure and define mapping rules to the new data model. I run the migration in a test environment, verify the results with you and then go live in a controlled way. I follow the same steps when moving legacy applications to modern architectures.

How is API security handled?

I never publish APIs without authentication and authorization. Depending on the need I use OAuth 2.0 / OpenID Connect, API keys or your in-house single sign-on (SSO) infrastructure. Together with measures such as rate limiting, input validation and activity logs, I make sure sensitive data is exposed only to authorized systems.

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