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I will fix or build java spring boot backend apis
Siyu Ren
About this gig
Need a Spring Boot backend fixed, improved, or extended?
I help developers fix Java backend issues including startup errors, REST API bugs, database problems, and integration failures.
I build Java REST APIs and backend modules with validation, error handling, database access, transactional logic, JWT authentication, role-based access, ownership checks, and focused tests.
Depending on the package, I work with MyBatis or MyBatis-Plus, MySQL or PostgreSQL, database migrations, API documentation, Docker packaging, and integrations.
My self-built food-ordering case demonstrates server-side price checks, atomic stock deduction, transactional order creation, idempotency, fulfillment logic, and rejection-path tests. I also have experience extending multi-module Spring Boot systems.
Each order is limited by agreed endpoints, data models, roles, and acceptance criteria. Frontend work, OAuth2/SSO, payments, Kubernetes, high availability, and security audits are not included by default.
Please message me before ordering with your Java and Spring Boot versions, endpoint list, database, roles, and expected delivery.
Get to know Siyu Ren
Siyu Ren
AI App Troubleshooting and Backend Developer
- FromChina
- Member sinceJul 2026
- Avg. response time1 hour
Languages
Chinese, English
I help founders rescue and stabilize AI-built web apps and backend systems. I diagnose deployment failures, Supabase Auth/RLS problems, API and database bugs, and Spring Boot issues, then deliver tested fixes with clear handover notes. My stack includes Lovable, Bolt, Replit, React, Vite, Supabase, Vercel, Java, Spring Boot, REST APIs, PostgreSQL, MySQL, Redis, and n8n. With 8 years of backend experience, I focus on root-cause analysis, secure access, clear scope, and practical fixes without unnecessary rebuilding.
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FAQ
Can you build a complete backend?
Yes, within an agreed module or backend slice. A full platform requires review and a custom offer.
Can you add JWT and role-based access?
Yes. Please provide the required roles and endpoint access matrix. I implement and test the agreed authentication, role, and ownership boundaries.
Can you work with an existing Spring Boot project?
Yes. I first review the Java and Spring Boot versions, structure, database access, authentication, tests, and current build status.
Which databases and persistence tools do you support?
I work with MySQL or PostgreSQL and with MyBatis or MyBatis-Plus within the agreed schema and query scope.
Is Docker deployment included?
Docker packaging is included only when listed in the package or custom offer. Hosting, CI/CD, Kubernetes, and production operations are separate.
Do you provide tests?
Yes. I provide focused tests for the agreed business flow and rejection paths. Load tests, penetration tests, and formal security audits are separate.
Do you need production secrets?
No. Do not send passwords, tokens, private keys, internal URLs, or production data. Sanitized samples and placeholder environment variables are enough for review.
