When recruiting an API developer, experience in the design and implementation of APIs, especially RESTful and GraphQL, is crucial. The candidate should demonstrate the ability to create scalable and secure APIs that are easy to integrate and maintain.

It is important that the API developer has solid programming skills in back-end technologies such as Node.js, Java, Python, or .NET. Familiarity with these technologies allows you to effectively create the business logic that is central to the functionality of the API.

The candidate should have experience working with various database systems, both SQL (e.g. MySQL, PostgreSQL) and NoSQL (MongoDB, Cassandra). The ability to optimally design data schemas and queries is essential to ensure the performance and scalability of API services.

API security is key, especially when handling sensitive data. The candidate should be familiar with security best practices such as authentication, authorisation, data encryption and techniques to prevent common attacks, e.g. SQL Injection, Man in the Middle, etc.

The API developer should be familiar with DevOps tools such as Docker, Kubernetes, Jenkins, which supports continuous integration and software delivery. The ability to work with these tools facilitates test automation, deployment and infrastructure management.

The ability to create accurate and understandable API documentation is essential. The documentation should be clear enough that other developers can easily use the API without additional support. The candidate should be proficient in tools such as Swagger or Postman.