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Metashrew

Metashrew is an open source indexer stack for building bitcoin metaprotocols. It significantly simplifies the architecture and implementation of complex metaprotocols on Bitcoin L1, providing a comprehensive foundation for smart contract development.

Metashrew is the core infrastructure that powers Alkanes smart contracts. It provides:

  1. Block Processing & Indexing:

    • Processes Bitcoin blocks and maintains indexes of relevant data
    • Supports deterministic indexing through WASM-based indexer programs
    • Ensures integrity through verifiable WASM binary hashes

  2. State Management:

    • Uses a key-value store (KeyDB) to maintain smart contract state
    • Handles state rollbacks during chain reorganizations
    • Provides historical state access at any block height

  3. Contract Execution:

    • Executes WASM-based smart contracts and indexers
    • Supports contracts written in Rust with Metashrew runtime bindings
    • Provides isolated execution environments for view functions
    • Enables nested WASM execution (WASM programs running within WASM environments)

  4. RPC Interface & View Layer:

    • Exposes contract view functions through RPC endpoints
    • Enables parallel processing of read operations
    • Supports comprehensive transaction simulation including:
      • Fuel cost computation
      • Balance sheet validation
      • Output prediction
      • Storage update previews
      • Historical state queries

Architecture Overview​

Metashrew consists of several key components:

  • Indexer: Processes Bitcoin blocks and maintains relevant indexes through WASM-based programs
  • KeyDB: Stores contract state and execution data
  • View Layer (metashrew-view):
    • Handles read-only contract function calls
    • Provides parallel processing capabilities
    • Ensures side-effect-free execution
  • WASM Runtime: Executes smart contract code and indexers in a sandboxed environment

For Developers​

As a smart contract developer, you'll primarily interact with Metashrew through:

  1. Deploying WASM contracts that define your smart contract logic
  2. Using the RPC interface to query contract state and execute view functions
  3. Integrating with the key-value store for state management

The platform handles all the complex infrastructure needed for Bitcoin smart contracts, allowing you to focus on writing contract logic and building your dApp.