Pass the Java
backend interview.
Structured Java backend interview questions and answers — Collections, OOP, PostgreSQL, Spring, DSA and system design. Every claim grounded in the JDK 25 Javadoc, the JLS and JEPs.
Framework Overview & Hierarchy
Modules
Roadmap →CoJava Collections Framework
15 topics · 89 Q · ~20h0%
Java Collections Framework
Lists, Sets, Maps, Queues, the equals/hashCode contract, concurrent collections, and the modern Sequenced Collections API. The single most-asked area in any Java interview.
OoObject-Oriented Programming
16 topics · 89 Q · ~24h0%
Object-Oriented Programming
The four pillars, equals/hashCode, immutability, SOLID, GoF design patterns, and modern Java 25 OOP (records, sealed classes, pattern matching). About 30% of any senior Java interview.
CcConcurrency & Multithreading
12 topics · 76 Q · ~45h0%
Concurrency & Multithreading
Threads, the Java Memory Model, locks, atomics, executors, CompletableFuture, synchronizers, deadlock, and virtual threads (Loom) — the #1 senior Java filter, from middle to senior interview depth.
PgPostgreSQL
15 topics · 123 Q · ~40h0%
PostgreSQL
Relational database internals, query optimization, indexing, transactions, and operational concerns for backend interviews.
SpSpring Framework & Spring Boot
16 topics · 142 Q · ~50h0%
Spring Framework & Spring Boot
Spring Core, Boot, Data, Security, and internals — from middle to senior interview depth.
DsData Structures & Algorithms
20 topics · 219 Q · ~80h0%
Data Structures & Algorithms
Language-agnostic algorithmic foundations with Java examples and Java Collections mapping. Big-O, classic data structures, algorithm paradigms, and interview pattern recognition.
LlLow-Level Design (LLD / OOD)
21 topics · 32 Q · ~40h0%
Low-Level Design (LLD / OOD)
Object-oriented system design at the class level. Machine-coding round preparation: classic problems with full solutions, class diagrams, design-pattern application, and trade-off discussion.
HlHigh-Level Design (HLD / Distributed Systems)
28 topics · 70 Q · ~60h0%
High-Level Design (HLD / Distributed Systems)
Distributed systems and large-scale architecture interview preparation. Fundamentals (CAP, consistency, replication), building blocks (caches, queues, databases), and full system designs across FAANG, EU, and regional interview styles.