Awesome CRDT

Overview

Awesome CRDT provides a comprehensive collection of resources for understanding and implementing Conflict-free Replicated Data Types (CRDTs). CRDTs enable distributed systems to achieve strong eventual consistency without coordination, making them ideal for offline-first applications and real-time collaboration.

Features

• CRDT Implementations: Yjs, Automerge, RON, Diamond Types
• Research Papers: Academic foundations and latest research
• Tutorials and Guides: Learn CRDT theory and practice
• Type Variants: Counters, registers, sets, lists, trees, text
• Language Support: JavaScript, Rust, Go, Python implementations
• Use Cases: Collaborative editing, distributed databases, P2P apps
• Performance Analysis: Benchmarks and optimization techniques

CRDT Fundamentals

What are CRDTs?

Conflict-free Replicated Data Types are data structures that can be replicated across multiple computers in a network, where replicas can be updated independently and concurrently without coordination, and it is always mathematically possible to resolve inconsistencies that might result.

Types of CRDTs

Operation-based CRDTs (CmRDTs)

• Communicate operations between replicas
• Require reliable broadcast
• Generally more efficient
• Examples: Operation-based counters, sets

State-based CRDTs (CvRDTs)

• Communicate full state between replicas
• Work with unreliable networks
• Simpler to reason about
• Examples: G-Counter, PN-Counter, LWW-Register

CRDT Data Types

Basic Types

Counters

• G-Counter: Grow-only counter
• PN-Counter: Positive-negative counter
• Use cases: View counts, likes, distributed counting

Registers

• LWW-Register: Last-Write-Wins register
• MV-Register: Multi-value register
• Use cases: Configuration values, user profiles

Sets

• G-Set: Grow-only set
• 2P-Set: Two-phase set (add/remove)
• OR-Set: Observed-remove set
• Use cases: Tags, categories, memberships

Complex Types

Sequences and Lists

• RGA: Replicated Growable Array
• LSEQ: List CRDT for collaborative editing
• Use cases: Ordered lists, document structure

Text Editing

• WOOT: Without Operational Transform
• RGA for text
• Use cases: Collaborative text editors

Trees and Graphs

• Replicated trees
• JSON CRDTs
• Use cases: Hierarchical data, documents

Popular Implementations

Yjs

• Language: JavaScript/TypeScript
• Features: High performance, small update size
• Use Cases: Collaborative editors (ProseMirror, CodeMirror, Monaco)
• Network: Supports WebRTC, WebSocket, IPFS
• Bindings: React, Vue, Angular, Svelte

Automerge

• Language: Rust with JS bindings
• Features: JSON-like API, full history
• Use Cases: Document collaboration, local-first apps
• Storage: Efficient binary format
• Sync: Network-agnostic sync protocol

RON (Replicated Object Notation)

• Language: Multiple implementations
• Features: Causal consistency, time travel
• Use Cases: Distributed databases, games
• Protocol: Self-contained operations

Diamond Types

• Language: Rust
• Features: Extremely fast, minimal memory
• Benchmarks: Fastest text CRDT implementation
• Use Cases: Performance-critical applications

Loro

• Language: Rust with WASM
• Features: Next-generation performance
• Use Cases: Modern collaborative apps
• API: Developer-friendly interface

Use Cases

Collaborative Editing

• Google Docs-like functionality
• Code collaboration (VS Code Live Share)
• Rich text editors
• Whiteboarding applications

Offline-First Applications

• Mobile apps with sync
• Desktop applications
• Progressive web apps
• Field data collection

Distributed Systems

• Distributed databases (Riak, Cosmos DB)
• Edge computing
• P2P networks
• IoT device coordination

Real-Time Applications

• Chat applications
• Multiplayer games
• Collaborative design tools
• Shared dashboards

Research and Theory

Foundational Papers

• "Conflict-free Replicated Data Types" by Shapiro et al.
• "A Comprehensive Study of CRDTs" by Shapiro et al.
• "Delta State Replicated Data Types" by Almeida et al.

Recent Research

• List CRDT optimizations
• Tree CRDTs
• Rich text CRDTs
• CRDT composition

Implementation Considerations

Performance

• Operation complexity
• Memory overhead
• Network bandwidth
• Garbage collection

Correctness

• Strong eventual consistency
• Causality preservation
• Idempotence
• Commutativity

Practical Concerns

• Tombstone management
• History pruning
• Schema evolution
• Migration strategies

Tools and Libraries

Testing and Visualization

• CRDT visualization tools
• Property-based testing
• Consistency checkers
• Benchmarking suites

Integration

• Database adapters
• Network protocols
• Persistence layers
• Monitoring tools

Resources

• CRDT.tech website
• Local-First Web development
• Martin Kleppmann's lectures
• Ink & Switch research

Pricing

Free and open-source resource.