Beyond FRAME - Crafting Custom Blockchains with Substrate's Core

The blockchain landscape is ever-evolving, with the demand for custom solutions driving innovation at every level. Substrate, a powerful framework from Parity Technologies, has emerged as a leader in enabling developers to build bespoke blockchains. At sub0 Reset 2024, Krishna Singh, a senior blockchain engineer at Blog Deep Labs, presented a thought-provoking session titled “Beyond FRAME: Crafting Custom Blockchains with Substrate’s Core.” This article explores the key insights from the session, focusing on Substrate’s core architecture, its modular design, and how developers can transcend traditional FRAME-based approaches to create highly tailored blockchain solutions.

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Understanding Substrate’s Core Architecture

Substrate’s modular architecture provides unparalleled flexibility for blockchain development. Its design separates the client-side code (node logic) from the runtime (blockchain logic), enabling independent development and testing. At its heart, Substrate operates through various components that work in harmony:

Key Components of Substrate:

1. RPC Server
   Acts as the interface for external interactions. It facilitates sending transactions and querying chain states via JSON-RPC, enabling users to access blockchain functionalities seamlessly.

2. Database
   An untyped key-value storage system that holds all chain data, including balances and proposals. This opaque structure ensures runtime logic dictates the interpretation of stored values.

3. Transaction Pool
   Manages incoming transactions by validating, sorting, and prioritizing them. It performs nonce checks, fee assessments, and signature verifications before routing transactions to execution.

4. Wasm Runtime
   The runtime contains the blockchain’s core logic, executed in a WebAssembly (Wasm) environment. It ensures determinism, compactness, and upgradeability without altering the underlying node binary.

5. Host Functions
   These serve as a bridge, allowing runtime logic to perform low-level operations such as cryptographic computations or storage interactions through the client-side node.

6. Runtime APIs
   Define interfaces for node-to-runtime communication, enabling seamless interactions such as querying state or executing transactions.

7. Import Queue
   Manages incoming blocks from peers, ensuring they are validated and meet consensus requirements before being added to the chain.

Beyond FRAME: Why Custom Solutions Matter

FRAME (Framework for Runtime Aggregation of Modularized Entities) is a Substrate development framework designed for rapid prototyping of blockchain applications. While FRAME is versatile and user-friendly, some use cases demand a more granular approach that avoids reliance on predefined pallets. Krishna Singh emphasized that by bypassing FRAME, developers can unlock:

• Greater Customization: Tailored runtimes that address unique business logic.
• Enhanced Performance: Minimized overhead by avoiding extraneous pallet logic.
• Deep Understanding: Insight into Substrate’s primitives, fostering a robust knowledge of blockchain mechanics.

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System Interactions: The Communication Pathways

Understanding the interplay between Substrate’s components is vital for crafting custom solutions. Singh detailed two primary communication pathways:

1. Node to Runtime Communication
   Nodes use runtime APIs to query states or submit transactions. For example, querying an account balance involves the RPC server passing the request to the runtime, which fetches the data from the database using host functions.

2. Runtime to Node Communication
   When the runtime needs to perform external tasks, such as signature verification or cryptographic hashing, it invokes host functions. This interaction enables the runtime to leverage the computational power of the node without overburdening the Wasm environment.

The Transaction Lifecycle: From Submission to Finalization

Singh broke down the lifecycle of a transaction to illustrate Substrate’s inner workings:

1. Submission
   A user submits a transaction via the RPC server, which forwards it to the transaction pool for validation.

2. Validation
   The transaction pool checks the transaction’s nonce, fee sufficiency, and signature validity. Valid transactions are queued for execution.

3. Execution
   The block proposer fetches transactions based on priority, initializes the block, and sequentially applies extrinsics. Each extrinsic updates a temporary state overlay.

4. Finalization
   Once all extrinsics are processed, the finalized block’s state is committed to the database, completing the lifecycle.

Core APIs for Custom Runtime Development

Developers venturing beyond FRAME must implement essential runtime APIs to define blockchain logic. Singh highlighted the following APIs:

• Version: Specifies the runtime version running on the node.
• Initialize Block: Prepares the runtime with the block header.
• Validate Transaction: Ensures a transaction meets all requirements before execution.
• Apply Extrinsic: Executes a single transaction and updates the state overlay.
• Finalize Block: Commits changes from the overlay to the main state database.

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A Practical Demonstration: Building a Fungible Token Blockchain

Singh showcased a custom blockchain implementation using Substrate’s minimal node template. The example featured a simple fungible token module, illustrating how core APIs and host functions work together. Key functionalities included:

1. Minting Tokens

   • Host functions fetched the receiver’s balance from storage.
   • Updated balances were written back using host functions.

2. Transferring Tokens

   • Balances of sender and receiver were fetched and validated.
   • Transactions failing balance checks returned appropriate errors without altering the state.

This demonstration underscored the importance of understanding Substrate’s primitives for implementing custom logic effectively.

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Unlocking Substrate’s Potential with Blog Deep Labs

Blog Deep Labs, where Krishna Singh serves as a senior blockchain engineer, has been instrumental in advancing Substrate adoption. With over 300 teams guided on Polkadot use cases and architecture, the lab combines technical expertise with real-world project delivery.

Their work highlights the potential of Substrate for crafting bespoke blockchains, enabling organizations to innovate without being confined by predefined frameworks.

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Conclusion: The Future of Custom Blockchain Development

Substrate’s modularity and flexibility position it as a cornerstone for blockchain innovation. Moving beyond FRAME allows developers to harness Substrate’s core capabilities, crafting solutions tailored to unique requirements. Krishna Singh’s session at sub0 Reset 2024 provided a comprehensive roadmap for this journey, combining theoretical insights with practical demonstrations.

As the blockchain ecosystem evolves, the ability to create deeply customized solutions will be a defining factor for success. Substrate, with its robust architecture and unparalleled flexibility, is poised to remain at the forefront of this revolution.