Mock Interview 8+ year Experience Java Developer | Spring Boot | Microservices | Code Decode

Context

• Mock interview session on Code Decode with Atul Shokar — senior Java backend developer (8+ years).
• Series invites participants via a Google form (link in video description).
• Option to request coding-round follow-up or mock interviews for other experience levels.

Key technologies, tools and concepts discussed

Core stack

• Java (primarily Java 8, some Java 11)
• Spring Framework and Spring Boot
• Microservices architecture

Build, repositories and branching

• Maven for builds
• Git (GitHub/Bitbucket)
• Branching strategy: develop, release, master
• Pull requests (PRs) and code review workflow

CI/CD and quality gates

• Jenkins pipelines: build, unit tests, SonarQube, security scans
• Nexus as artifact registry
• Automated deploys per branch/environment
• Terraform for infrastructure-as-code

Containerization and orchestration

• Docker: Dockerfile packs JAR, JDK, runtime and libraries
• Docker image versioning per application version
• Container registries: Nexus or AWS container registry
• Kubernetes for managing pods and containers

Cloud and deployment

• AWS (ECS used in examples)
• CloudWatch for logs and alarms
• Experience with PCF (Pivotal Cloud Foundry) in one project

Observability and logging

• Kibana/ELK and Splunk for centralized logs and troubleshooting
• CloudWatch also used
• Emphasis on searching logs by application or unique identifiers

REST and inter-service communication

• Service discovery: Eureka server
• Client-side load balancing: Ribbon and Feign (Feign preferred for service-to-service calls)
• RestTemplate for external (third-party) HTTP calls
• Synchronous vs asynchronous communication:
  • HTTP for synchronous calls
  • Messaging systems (example: IBM MQ) for asynchronous flows

Resilience and fault tolerance

• Circuit breaker pattern (Resilience4j) with fallback behaviors
• Horizontal scaling; alarms to trigger autoscaling
• Scale high-demand services (e.g., search) independently

Distributed transactions

• Saga pattern awareness for multi-service transaction management (orchestration vs choreography)
• Two-Phase Commit (2PC) mentioned but noted as less commonly used
• Recommended to learn why Saga is preferred and differences vs 2PC

Security

• JSON Web Tokens (JWT) discussed
• High-level mention of OAuth2 (authorization server + resource server)
• Interviewer emphasized deeper understanding required (end-to-end flows, token issuance/validation)
• Risk: actuator endpoints can expose sensitive internals — manage actuator exposure and ports

Spring Boot specifics

• Actuator:
  • Add spring-boot-starter-actuator
  • Configure exposed endpoints in application.properties
  • Common endpoints: health, beans, autoconfig
  • Management port vs application server port; avoid exposing actuator endpoints without protection
• AOP:
  • Candidate had limited hands-on experience
  • Use-cases: cross-cutting concerns like logging, timing, exception handling
• Exception handling:
  • Use @ControllerAdvice with @ExceptionHandler for global handling
  • Avoid duplicating try-catch across layers
• Spring profiles and central config:
  • Config server for environment-specific properties versus repeating properties per microservice

Testing

• Unit testing: JUnit and Mockito
  • Mock dependencies to avoid hitting real DBs or external services (cost, performance, consistency)
• Integration/BDD:
  • Cucumber mentioned for BDD-style integration tests; candidate had limited hands-on experience

Design patterns and principles

• Common patterns used: Builder, Singleton, Factory
  • Examples: Builder for classes with many fields; Singleton for heavy shared resources (EntityManager, DB driver, logger)
• SOLID principles discussed at a high level
  • Recommended to prepare concrete examples for each principle

PR / code-review checklist (items highlighted in interview)

• Code compiles and unit tests pass (Jenkins gates)
• SonarQube/code-quality and security scan compliance
• Correct naming conventions and appropriate data structures (e.g., prefer ArrayList unless LinkedList is required)
• Avoid duplication; apply Single Responsibility Principle and refactor duplicate logic into utilities
• Correct layering (no business logic in entities)
• Use design patterns where appropriate
• Ensure heavy objects (EntityManager/DB client) are managed correctly (singleton if applicable)
• Documentation/comments for new methods; follow project conventions
• Consider impact on other services and potential side effects

Interviewer feedback — areas to strengthen (actionable)

• Deepen hands-on Terraform knowledge if you mention it — expect DevOps-focused questions
• Know actuator configuration and how to secure actuator endpoints (separate management port, authentication)
• Learn practical AOP use-cases (timing, logging) and how to implement them
• Understand end-to-end OAuth2/JWT flow: authorization server, resource server, token issuance and validation
• Study Saga pattern vs 2PC; know when and why Saga is preferred
• Be prepared to explain Mockito usage with clear examples (why mock: cost, speed, isolation)
• Only claim BDD/Cucumber experience if you can demonstrate hands-on scenarios
• Be able to describe CI/CD pipeline stages and how rollback/versioning of Docker images is handled

Miscellaneous / process notes

The interviewer praised that Atul could speak to most items listed on his resume — important interview advice: include only technologies you know and be prepared for deeper follow-ups.

• Offer from the channel: viewers can request follow-up videos (coding rounds) or specific experience-level mock interviews via comments

Main speakers / sources

• Atul Shokar — candidate, senior Java backend developer (8+ years)
• Interviewer / host — Code Decode (unnamed host providing questions and feedback)