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I will build and fix your java spring boot rest API
Sylvain REY
About this gig
Need a Java Spring Boot backend that works and stays maintainable? I fix bugs and build features in Spring Boot REST APIs, from a single failing endpoint to a complete module.
What I do:
Bug fixes in Spring Boot, Spring Data JPA and Spring Security.
New REST endpoints with validation and clean error handling.
PostgreSQL persistence and query tuning.
Unit and integration tests with JUnit and Mockito.
A short written summary of what changed and why.
About me: senior backend engineer with about 7 years of Java and Spring in production, including a regulated fintech platform (accounts, swaps, AML checks). I work with Git, Docker and standard CI pipelines.
How it works: send me repository access or a zip and describe the issue or the feature. I confirm scope, price and delivery before starting. You receive a pull request or patch with tests.
Not included: front-end work. If your task is larger than these packages, message me before ordering and I will send a custom offer.
Get to know Sylvain REY
Sylvain REY
Senior Backend and Blockchain Engineer
- FromUnited States
- Member sinceApr 2025
Languages
English, French, Spanish
Senior backend engineer for fintech and blockchain teams.
7 years of Java and Spring Boot in regulated environments (payments, ledgers, KYC/AML). 3 years on EVM chains: event indexers, reorg handling, Kafka and PostgreSQL pipelines.
What I deliver: backend features and APIs, EVM indexers, and written architecture reviews of fintech and crypto backends, with risks ranked and fixes you can ship.
Scope and price agreed in writing before I start. Tests and documentation with every delivery. English, French, Spanish.
My Portfolio
FAQ
Which Java and Spring Boot versions do you work with?
Java 8 to 21 and Spring Boot 2.x and 3.x. If your project is on an older version, tell me before ordering and I will check it first.
How do you access my code and keep it safe?
Through a private repository invite or a zip, whichever you prefer. I only use your code for your task, and I can work with a limited-access account.
