You will get a secure Spring Boot REST API in Kotlin or Java
Project details
I will build or extend a secure Spring Boot REST API using Kotlin or Java.
Depending on the selected package, the implementation can include request validation, structured error handling, business logic, PostgreSQL persistence with JPA or R2DBC, JWT authentication, Spring Security, OpenAPI documentation, Docker configuration, and automated unit or integration tests.
I have 8+ years of JVM software engineering experience and have built production backend systems with Spring Boot MVC, WebFlux, Kotlin Coroutines, Project Reactor, PostgreSQL, Redis, RabbitMQ, Resilience4j, Testcontainers, and Docker.
I can work inside an existing codebase or create a clean new service using layered, Clean, or Hexagonal Architecture. The implementation will follow the agreed API contract and existing project conventions.
Upwork labels endpoint count as “Number of Pages” in this category. For this project, each listed page represents one REST endpoint.
Please provide the endpoint requirements, data model, security rules, repository access, and external API documentation when applicable.
Depending on the selected package, the implementation can include request validation, structured error handling, business logic, PostgreSQL persistence with JPA or R2DBC, JWT authentication, Spring Security, OpenAPI documentation, Docker configuration, and automated unit or integration tests.
I have 8+ years of JVM software engineering experience and have built production backend systems with Spring Boot MVC, WebFlux, Kotlin Coroutines, Project Reactor, PostgreSQL, Redis, RabbitMQ, Resilience4j, Testcontainers, and Docker.
I can work inside an existing codebase or create a clean new service using layered, Clean, or Hexagonal Architecture. The implementation will follow the agreed API contract and existing project conventions.
Upwork labels endpoint count as “Number of Pages” in this category. For this project, each listed page represents one REST endpoint.
Please provide the endpoint requirements, data model, security rules, repository access, and external API documentation when applicable.
Programming Languages
Java, KotlinCoding Expertise
Performance Optimization, SecurityWhat's included
| Service Tiers |
Starter
$99
|
Standard
$299
|
Advanced
$599
|
|---|---|---|---|
| Delivery Time | 3 days | 7 days | 14 days |
Number of Revisions | 1 | 2 | 2 |
Number of Pages | 1 | 3 | 5 |
Design Customization | - | - | - |
Content Upload | - | - | - |
Responsive Design | - | - | - |
Source Code |
Optional add-ons
You can add these on the next page.
Fast Delivery
+$50 - $300
Additional Revision
+$75
Additional REST Endpoint
(+ 2 Days)
+$99Frequently asked questions
About Andrii
Android/Kotlin Developer | Compose, BLE, KMP, Spring Boot, React & AI
Orhei, Moldova - 2:10 pm local time
I have 8+ years of Android development experience with Kotlin and Java. I have worked on and maintained 30+ production apps across logistics, agritech, healthcare, fitness, e-commerce, telematics, and hardware-connected products.
I can help you with:
• Fixing crashes, ANRs, memory leaks, performance issues, and unstable builds
• Developing Android features with Kotlin and Jetpack Compose
• Modernizing legacy Java/XML applications
• Migrating to Clean Architecture, MVVM, MVI, and modular architecture
• Bluetooth Classic, BLE, GATT, ELD, and telematics integrations
• Kotlin Multiplatform applications for Android and iOS
• REST APIs, Firebase, authentication, payments, maps, and third-party SDKs
• Room, SQLDelight, SQLite, DataStore, and offline-first functionality
• Gradle, dependencies, CI/CD, signing, and Play Store releases
• Unit, integration, and UI testing
Selected Android experience:
• SprayScan / Spray Assist: Native Android application built with Kotlin, Jetpack Compose, OpenCV, Hilt, Room, and Clean Architecture. The application performs on-device spray coverage analysis using computer vision.
• EldKey and Report: Kotlin Multiplatform applications with shared business logic, Ktor networking, SQLDelight storage, Koin, native iOS integration, and real-time Bluetooth hardware communication.
• Agritech and commercial applications: Worked on and maintained applications for ADAMA, Corteva, Arysta, NuFarm, DILA, Gymmy/Sportlife, and other products.
Backend and frontend development:
I can also build, maintain, and troubleshoot complete web platforms. My backend stack includes Kotlin, Java, Spring Boot, WebFlux, Spring MVC, PostgreSQL, MySQL, Redis, Elasticsearch, WebSocket, JWT, OAuth2, RabbitMQ, Docker, and REST APIs.
For frontend development, I work with React, TypeScript, React Router, Redux Toolkit, TanStack Query, Vite, and responsive web interfaces.
AI assistants and integrations:
I build AI assistants using Python, FastAPI, RAG, LangGraph, LangChain, Qdrant vector search, LiteLLM, and asynchronous RabbitMQ workflows.
For Calista, I built a stateful RAG assistant integrated with a Spring Boot backend and React frontend. The platform also uses PostgreSQL, Redis, Elasticsearch, MinIO, analytics integrations, and Docker-based deployment.
This cross-platform experience is useful when you need one engineer who can trace an issue from the Android device through the API, backend service, database, web dashboard, or AI assistant.
I am comfortable joining existing codebases, investigating difficult issues, reviewing architecture, and delivering changes in small, testable milestones.
Send me the current issue, repository state, and expected result. I can review the scope and propose a clear first milestone.
Steps for completing your project
After purchasing the project, send requirements so Andrii can start the project.
Delivery time starts when Andrii receives requirements from you.
Andrii works on your project following the steps below.
Revisions may occur after the delivery date.
Review requirements and API contract
I will review the business rules, endpoints, data model, security requirements, existing codebase, and expected request and response formats.
Design the backend implementation
I will define controllers, DTOs, validation, services, persistence, error handling, and database changes required by the selected package.