M.Talim
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Redis Server in Java

Distributed Systems from Scratch (Challenge Overview)

Built a Redis-compatible in-memory data store in Java, replicating core Redis functionality including data structures, persistence, replication, transactions, and real-time messaging — all from scratch.

🔧 What It Does

  • Implements RESP (Redis Serialization Protocol) for communication with clients
  • Supports core Redis data types: strings, lists, sorted sets, and streams
  • Implements Pub/Sub, transactions, and key expiration
  • Enables master-slave replication and RDB persistence loading
  • Supports blocking operations and thousands of concurrent clients using Java Virtual Threads

🚀 Key Features

  • String ops (GET, SET, INCR) with optional expiration
  • List ops (LPUSH, LRANGE, BLPOP)
  • Sorted Set ops (ZADD, ZRANGE, ZREM)
  • Stream ops (XADD, XREAD, XRANGE)
  • Pub/Sub (SUBSCRIBE, PUBLISH)
  • Replication (PSYNC, REPLCONF) and transaction support (MULTI, EXEC)
  • RDB loading and time-based key expiry
  • Runs using Java 21’s Project Loom (virtual threads)

🏗️ Tech Stack

  • Language: Java 21
  • Concurrency: Virtual threads (Project Loom), ReentrantLock, ConcurrentHashMap
  • Networking: Custom TCP server with RESP protocol support
  • Design Patterns: Command pattern, layered architecture, modular command routing

💡 Why It’s Interesting

  • Mirrors real-world Redis behavior with protocol-level compatibility
  • Explores low-level systems programming in Java
  • Exercises deep knowledge of networking, concurrency, and protocol design
  • Builds foundational experience in distributed system components like replication and messaging

🧠 Key Learnings

  • Implementing a binary protocol (RESP) and ensuring spec compliance
  • Managing lightweight concurrency using Java virtual threads
  • Handling blocking commands without freezing the main thread (e.g. BLPOP, XREAD)
  • Designing a transaction-safe, multi-type in-memory database
  • Building and debugging a real-time replication mechanism

✅ TL;DR

Recreated a Redis-compatible server from the ground up in Java, with support for advanced features like replication, streams, and transactions — all using modern Java concurrency (virtual threads).