Comprehensive List of Technical Interview Questions for BAT (First, Second, Third Rounds)

Below is a compiled set of technical interview topics commonly asked in BAT (Baidu, Alibaba, Tencent) interviews, organized by interview round.

First Round

OSI seven-layer and five-layer network models and protocols per layer.

Deadlock conditions, avoidance techniques, Banker's algorithm, and resolution methods.

How to detect a cycle in a linked list.

JVM class loading mechanism, parent delegation model, and its rationale.

JVM tuning parameters.

Principles of autoboxing and unboxing.

JVM garbage collection algorithms.

CMS and G1 collectors.

Differences between HashSet and HashMap, underlying implementation of put, resizing, thread safety in ConcurrentHashMap, differences between Java 7 and 8.

Principles of MD5 encryption.

Various ways to block a thread.

Synchronized vs ReentrantLock.

AQS framework, CountDownLatch, CyclicBarrier, Semaphore, read‑write lock.

Second Round

B‑Tree index, differences between MyISAM and InnoDB indexes.

Application scenarios of BIO and NIO.

Explanation of ThreadLocal.

Database isolation levels, implementation methods, three‑phase locking protocol, shared vs exclusive locks, MVCC, gap locks.

Database indexing, B+ tree, why indexes are needed, suitable fields, impact on insert/delete performance and mitigation.

Database table design, normalization forms, design considerations.

Shared vs non‑shared locks, visibility of data locked by one transaction to another.

Spring bean lifecycle, default singleton scope, how to configure non‑singleton beans.

Third Round

Rate limiting strategies under high concurrency.

Thread pool rejection policies.

Spring Boot startup process.

Differences and relationships among clustering, load balancing, distributed systems, and data consistency.

Principles for vertical and horizontal database sharding, when to apply each, and sizing thresholds.

Design principles and use cases of Redis, Kafka, and Dubbo.