Java & Spring Boot interview questions — Level IV · Senior

16 questions with a short answer, a full explanation and the mistakes interviewers listen for. Every question has a difficulty level from I (Beginner) to V (Expert).

Variables, Data Types & Operators · Java Foundations — Zero to Basics

• Explain the difference between the stack and the heap and how it relates to garbage collection and escape analysis.IV

Strings, StringBuilder & String Pool · Java Foundations — Zero to Basics

• Why can holding a substring or splitting large strings cause memory issues, and how do you avoid related leaks?IV

Generics — Wildcards, Bounded Types, PECS · Java Foundations — Zero to Basics

• Why does Java warn about generic varargs (heap pollution), and what does @SafeVarargs actually assert?IV

JVM Architecture · JVM Internals & Runtime

• When and why would you deliberately break parent delegation with a custom or child-first class loader?IV

Scalability Fundamentals · System Design

• How do CAP and its practical cousin PACELC actually drive a design decision?IV

Microservice Patterns & Architecture · Distributed Systems & Messaging

• A team wants to split a young product into microservices. What pushback and guidance would you give?IV
• Each microservice owns its data, but a feature needs a join across three services. How do you design it?IV
• What's the difference between liveness and readiness checks in a service mesh / orchestrator, and why conflate them at your peril?IV

Multi-Module Maven Project Design · Real-World Java Backend Architecture

• How do you actually enforce module boundaries so they don't erode over time?IV
• How does a clean multi-module layout make a future move to microservices easier or harder?IV

Creational Design Patterns · Design Patterns in Java

• You see a Builder on a two-field DTO. What's your reaction, and when is a Builder genuinely warranted?IV

JVM Internals — Top Interview Q&A · Interview Rapid-Fire — Top Q&A

• How do you identify memory leaks in production?IV
• What is a Heap Dump and when would you analyze it?IV
• How do you troubleshoot high CPU usage in JVM applications?IV
• What tools do you use for JVM performance analysis?IV

Start Here — Build Your First AI Feature · Build AI Features as a Java Backend Engineer

• Why can the same prompt give different answers, and what levers control that variability in a backend service?IV