Backend Developer (Java/Kotlin)
Developing enterprise-grade backend services in Java/Kotlin with a focus on reliability and scalability
Backend Developer (Java/Kotlin) is a role in the Backend Engineering family. It has 74 skills across 5 levels (from Junior to Principal). 217 skills are mandatory. Key domains: Programming Fundamentals, Backend Development, Database Management.
Technology Stack
Focus by Level
Building REST endpoints with Spring Boot. Writing unit tests (JUnit/Mockito). Working with JPA/Hibernate. Fixing bugs. Learning Spring ecosystem.
Designing and building microservices. Setting up Spring Security. Optimizing JPA queries. Working with message brokers. Code review. Migrating from Java to Kotlin.
Designing distributed systems. JVM tuning (GC, memory). Reactive programming (WebFlux). Building libraries and starters. Event-driven architecture design.
Domain system architecture. Spring Cloud microservices. Standards for Java/Kotlin development. Coordination with DevOps/Platform. Migrating legacy monoliths.
Enterprise architecture. Choosing JVM vs non-JVM for new systems. Modernization strategy. Company standards. Vendor management.
Skill Matrix
74 skills × 5 levels. Click on a cell for details.
AI-Assisted Development
4 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| GitHub Copilot | A | W | A | E | E |
| Cursor IDE | A | W | A | A | — |
| ChatGPT / Claude | A | W | A | E | E |
| Prompt Engineering for Code | A | W | A | E | — |
API & Integration
8 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| REST API Design | A | W | A | E | E |
| GraphQL Design | A | W | A | E | E |
| WebSocket API Design | A | W | A | E | E |
| gRPC & Protocol Buffers | A | W | A | E | E |
| gRPC & Protocol Buffers | A | W | A | E | E |
| API Versioning Strategies | A | W | A | E | E |
| API Documentation | A | W | A | E | E |
| Rate Limiting & Throttling | A | W | A | E | E |
Architecture & System Design
6 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| System Design Fundamentals | A | W | A | E | E |
| Microservices Decomposition | — | A | W | A | — |
| Clean Architecture | A | W | A | E | E |
| CQRS | A | W | A | E | E |
| Event-Driven Architecture | A | W | A | E | E |
| DDD Tactical Patterns | — | A | W | A | — |
Backend Development
8 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| Python Web Frameworks | A | W | A | E | E |
| Java Spring Ecosystem | A | W | A | E | E |
| Apache Kafka | A | W | A | E | E |
| RabbitMQ | A | W | A | E | E |
| Message Broker Patterns | A | W | A | E | E |
| Redis | A | W | A | E | E |
| Caching Strategies | A | W | A | E | E |
| Elasticsearch / OpenSearch | A | W | A | E | E |
Cloud & Infrastructure
6 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| Docker | A | W | A | E | E |
| Container Security Scanning | A | W | A | E | E |
| Kubernetes Core | A | W | A | E | E |
| Terraform | A | W | A | E | — |
| AWS | A | W | A | E | E |
| Network Fundamentals | A | W | A | — | — |
Database Management
9 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| PostgreSQL | A | W | A | E | E |
| MySQL / MariaDB | A | W | A | E | E |
| Database Indexing | A | W | A | E | E |
| Query Optimization | A | W | A | E | E |
| Transactions & Concurrency | A | W | A | E | E |
| Connection Pooling | A | W | A | E | E |
| Database Sharding | A | W | A | E | E |
| Data Modeling & Schema Design | A | W | A | E | E |
| Database Migrations | A | W | A | E | E |
DevOps & CI/CD
1 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| GitHub Actions / GitLab CI | A | W | A | E | E |
Observability & Monitoring
6 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| Structured Logging | A | W | A | E | E |
| ELK Stack | A | W | A | E | E |
| Prometheus & Grafana | A | W | A | E | E |
| OpenTelemetry | A | W | A | E | E |
| SLI / SLO / SLA | A | W | A | — | — |
| On-Call Management | A | W | A | E | E |
Performance Engineering
4 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| CPU Profiling | A | W | A | E | E |
| Memory Profiling | A | W | A | E | E |
| Latency Optimization | A | W | A | E | E |
| Performance Budgets | A | W | A | E | E |
Programming Fundamentals
10 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| Algorithms & Complexity | A | W | A | E | E |
| Data Structures | A | W | A | E | E |
| OOP & SOLID Principles | A | W | A | E | E |
| Design Patterns | A | W | A | E | E |
| Multithreading | A | W | A | E | E |
| Async Programming | A | W | A | E | E |
| Code Quality & Refactoring | A | W | A | E | E |
| Type Safety & Type Systems | A | W | A | E | E |
| Generics & Parametric Polymorphism | A | W | A | E | E |
| Memory Management | A | W | A | E | E |
Security
4 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| OWASP & Application Security | A | W | A | E | E |
| Secure Coding Practices | A | W | A | E | E |
| Secrets Management | A | W | A | E | E |
| JWT / OAuth2 / OIDC | A | W | A | E | E |
Testing & QA
5 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| TDD & BDD | A | W | A | E | E |
| Unit Testing | A | W | A | E | E |
| Integration Testing | A | W | A | E | E |
| E2E Testing | A | W | A | E | E |
| TestContainers | A | W | A | E | E |
Version Control & Collaboration
3 skills| Skills | Jun | Mid | Sen | Lead | Princ |
|---|---|---|---|---|---|
| Git Advanced | A | W | A | E | E |
| Code Review | A | W | A | E | E |
| Documentation as Code | A | W | A | E | E |
FAQ
What skills are needed for the Backend Developer (Java/Kotlin) role?
The Backend Developer (Java/Kotlin) role requires 74 skills, of which 217 are mandatory. Skills are distributed across 5 levels: from Junior to Principal. See full matrix.
How to advance to the next level in the Backend Developer (Java/Kotlin) role?
Use the Grade Calculator to assess your current level and get personalized recommendations. The system will show which skills need to be developed for the next level.
What tech stack is used in the Backend Developer (Java/Kotlin) role?
The stack includes 5 technologies at different levels. Java 21+/Kotlin 1.9+, Spring Boot 3.2+, PostgreSQL, JPA/Hibernate, Maven/Gradle, JUnit 5, Docker, Java 21+/Kotlin 1.9+, Spring Boot 3.2+, Spring Security, PostgreSQL/Redis, Kafka basics, Flyway, TestContainers, Docker Compose, CI/CD, Java 21+ (Virtual Threads)/Kotlin, Spring WebFlux, PostgreSQL/Redis/MongoDB, Kubernetes, Kafka/RabbitMQ, Micrometer/Prometheus, JFR, GraalVM native image...
How does the community define requirements for the Backend Developer (Java/Kotlin) role?
Role requirements are shaped by the community through a proposal system. Any member can suggest changes that go through voting and expert review.