The Disruptor pattern is a high-performance inter-thread messaging library and concurrency design pattern developed by LMAX—a low-latency financial exchange.

It’s designed to pass data between threads with minimal latency, avoiding the overhead of traditional queues, locks, or concurrent collections like BlockingQueue. The Disruptor achieves extreme throughput and low latency by using preallocated ring buffers and a lock-free, single-writer design.

Key Concepts

Ring Buffer

• A fixed-size circular array where data is placed by a single producer and consumed by one or more consumers.
• Memory is preallocated, so there's no allocation/deallocation during runtime (which eliminates GC pressure in managed languages like Java).

Sequencer

• Maintains a sequence number for each slot in the ring buffer.
• Producers and consumers coordinate using these sequence numbers instead of locks.

Memory Barriers / Fences

• Instead of using locks, Disruptor uses memory barriers to ensure visibility and ordering across CPU cores.
• This leverages mechanics of modern CPU caches for very fast coordination.

Single Writer Principle

• Only one thread writes to the ring buffer. This prevents contention and eliminates the need for complex synchronization.

Multiple Consumer Patterns

• Work processors (each consumer gets a subset of messages)
• Broadcast processors (each consumer sees every message, like an event bus)

Why It's Fast

• Avoids lock contention
• Preallocates memory
• Uses mechanical sympathy: carefully designed for CPU cache lines, memory barriers, and branch prediction
• Minimizes cache coherence traffic and false sharing

Typical Use Cases

• High-frequency trading systems
• Market data distribution
• Low-latency event pipelines
• Real-time analytics and telemetry

Comparison with Other Queues

Ecosystem

• Native implementation is in Java, but the concept has been ported to C++, Rust, Go, and more.
• Some libraries inspired by Disruptor include:
  • Chronicle Queue (Java)
  • Agrona (low-level library behind Disruptor)
  • Tranquility (Scala)

Real-World Example

LMAX used Disruptor to build a financial exchange that:

• Runs on a single-threaded business logic engine
• Handles 6 million orders per second
• With sub-millisecond end-to-end latency

If you're working in C++ or another systems language, Disruptor can serve as inspiration for a lock-free ring buffer with memory fences and cache-aware data structures. It's particularly powerful when paired with NUMA-awareness and low-latency OS tuning.