Senior Fullstack Engineer – API-First Integrations Lead

Codest Ltd. Company No. 12590542, VAT number: GB363431020; Poland; Remote; PLN 223,000 - 290,000; Full time

Benefits offered by this job

Worksmile platform access

Growth-focused environment

Job summary

The Codest is seeking an experienced software engineer for a New Ventures Core Tech project. You will design API contracts, enable partner integration, and drive frontend work on checkout paths using React.

Bridging Java (and Kotlin) backends with modern frontend practices, you will define standards for external B2B integrations, and ensure secure authentication (OAuth 2.0/OpenID Connect). English level B2+ required. This role is based in Poland on a B2B contract.

Qualifications

• Strong experience with Java and Kotlin backends.
• Proven ability to design, build and scale RESTful APIs with API-first design.
• Excellent frontend skills with modern JS/TS and React.
• Secure authentication practices (OAuth 2.0, OpenID Connect).
• Ability to define coding standards and lead technical discussions.

Responsibilities

• API Design & Partner Integration: design robust API contracts and docs, create mock environments.
• Frontend Development: build modern web interfaces (checkout, landing pages) consuming partner services.
• Technical Leadership: align Java backend design with frontend work for cohesive implementation.

Skills

Java

Kotlin

RESTful APIs

OpenAPI/Swagger

JavaScript/TypeScript

React

OAuth 2.0/OpenID Connect

English B2+

Job description

The Codest is seeking an experienced software engineer for a New Ventures Core Tech project. You will design API contracts, enable partner integration, and drive frontend work on checkout paths using React.

Bridging Java (and Kotlin) backends with modern frontend practices, you will define standards for external B2B integrations, and ensure secure authentication (OAuth 2.0/OpenID Connect). English level B2+ required. This role is based in Poland on a B2B contract.