Comprehensive Interview Review: Redis, MySQL, Networking, OS, and Java Fundamentals

Redis Overview

Redis is an in‑memory database offering extremely fast read/write operations, commonly used for caching, message queues, and distributed locks. It supports various data types (String, Hash, List, Set, Zset, Bitmaps, HyperLogLog, GEO, Stream) with atomic operations, provides persistence via AOF and RDB, and uses a single‑threaded I/O model supplemented by multi‑threaded I/O in version 6.0.

Why Redis Is Fast

Most operations run in memory, avoiding CPU bottlenecks; the single thread eliminates lock contention, and I/O multiplexing (select/epoll) allows one thread to handle many sockets.

Persistence Mechanisms

Redis can persist data using Append‑Only File (AOF) logging each write command, or RDB snapshots that dump the memory state to disk.

Distributed Lock with Redis

SET lock_key unique_value NX PX 10000

Unlock safely with a Lua script that checks the stored value before deleting the key.

MySQL Fundamentals

Transaction properties (ACID): atomicity, consistency, isolation, durability. Persistence is ensured by redo logs, atomicity by undo logs, isolation by MVCC or locks.

Row‑level lock types: record lock, gap lock, next‑key lock.

Index types include B+Tree, hash, full‑text, clustered (primary) and secondary indexes; B+Tree is preferred for range queries because leaf nodes are linked.

Composite indexes follow the left‑most prefix rule; covering indexes allow queries to be satisfied from the index alone.

Network Fundamentals

Brief overview of the OSI seven‑layer model and the distinction between TCP (reliable, connection‑oriented) and UDP (connectionless). Explanation of forward and reverse proxy roles.

Operating‑System Concepts

Process virtual address space layout (code, data, BSS, heap, mmap, stack) and the purpose of each segment. Description of process and thread context switches and the role of the PCB.

Java vs Go

Comparison of syntax, concurrency model, performance, ecosystem, and developer experience.

Explanation of the volatile keyword for visibility and memory barriers.

Overview of Java garbage‑collection algorithms: mark‑sweep, copy, mark‑compact, and generational collection.

Interview Reflection

The interview focused on Redis, MySQL, networking, and OS fundamentals; algorithm questions were limited. The author notes the need for deeper database study and more algorithm practice.