Freelance Senior Java Developer

Amsterdam - Netherlands

Monthly Salary: Not Disclosed

Posted on: 9 hours ago

Vacancies: 1 Vacancy

Job Summary

Company Intro

AtToloka AIwe create data that powers leading GenAI models and innovations. We work with frontier labs big tech renowned AI startups enterprises and non-profit research organizations worldwide. We use a combination of Experts Crowd Tech Platform to teach AI models to reason and evaluate their efficacy and safety. We have experts in more than 50 different domainsfrom doctors and lawyers to physicists and engineersand boast one of the most diverse global crowdsrepresenting over100 countries and speaking 40 languages. We are a well-funded startup with an enviable portfolio of clients includingAnthropicAmazonMicrosoftpoolsideRecraft andShopify.

Recently we secured strategic investment led byBezos Expeditionswith participation fromMikhail ParakhinCTO of Shopifyand board advisor to leading GenAI companies who now serves as our Chairman of the Board. Our remote-first team is globally distributed around the world:USAUKthe NetherlandsIsraelCzech RepublicSerbia and more. We are headquartered in Amsterdam.

About the Role

We are looking for aFreelance Senior Java Developer who will take ownership of the design scalability and overall technical quality of our systems. This role goes far beyond simply writing code - its about architectural thinking deep understanding of backend systems and ensuring performance reliability and maintainability at scale.

Youll be responsible for shaping core components of our platform optimizing existing solutions and driving best practices across the engineering team. This position requires both strong hands-on development skills and the ability to think strategically about how different systems fit together to deliver long-term value.

What youll be doing

Leading the technical direction of the backend part of the projects;
Designing and reviewing system architecture to ensure scalability performance and reliability;
Writing high-quality production code and conducting code reviews;
Decomposing large features into smaller tasks and driving their successful delivery;
Ensuring consistency and compatibility of APIs across services (REST gRPC);
Contributing to clean maintainable and observable backend services;
Driving CI/CD pipelines testing and DevOps practices.

What you should know / be able to do

Senior-level expertise in Java and Spring Boot;
Strong experience in system design architecture and clean code practices;
Hands-on experience with PostgreSQL;
Solid experience with REST and gRPC API design and integration;
Experience working with containerized services and cloud deployments;
Practical experience with CI/CD tools (TeamCity GitHub Actions);
Ability to break down complex features and drive execution independently;
Excellent communication skills and ability to work as an individual technical leader.

Nice to have

Experience with Kubernetes Docker and Terraform;
Experience with high-load / performance-critical applications;
Experience with Temporal (workflow orchestration);
Experience with Redis Databricks;
Experience using AI code assistants (e.g. Cursor Claude Code Copilot etc.).

Who you are

A hands-on senior engineer who delivers end-to-end;
A systems thinker who can balance long-term architecture with fast delivery;
Pragmatic proactive and comfortable working in a fast-moving startup environment;
Open to feedback clear in communication and able to justify technical decisions.

What we can offer

Freelance contract (B2B);
Flexible payment based on the results of work;
Flexibility: we offer freelance collaboration. You will also design with your manager a workday that works best for you;
Friendly community.

Important Notice Scam Alert Regarding Fake Job Postings

It has come to our attention that an individual or group is fraudulently impersonating Toloka to post fake jobs and solicit personal information from be aware:

Official Communication:Our recruiting team willonlycontact you from an official email address. We will NEVER use Gmail Yahoo Tolokainc or other personal or seemingly business email accounts.
Our Process:We willneverask for your bank account details credit card number or any fees as part of the application or interview process.
Official Listings:All legitimate job openings are posted on our official careers page: to do:If you see a suspicious job posting or have been contacted by someone you suspect is a scammer please do not provide any personal information. Instead report the incident to us directly at and report the profile/post to are taking this matter very seriously and are working with the appropriate parties to resolve it.

Thank you for your vigilance!

Company IntroAtToloka AIwe create data that powers leading GenAI models and innovations. We work with frontier labs big tech renowned AI startups enterprises and non-profit research organizations worldwide. We use a combination of Experts Crowd Tech Platform to teach AI models to reason and evalua...