Smart Contract Developer Interview: How to Handle Logging and Gas Fees on Layer 2

To address logging and monitoring in Solidity smart contracts, especially for Layer 2, consider the following methods:

(1) Optimized Event Logging: You're already using emit events. To capture more granular data, try to minimize the number of events. Instead of emitting events for every state change, group related changes into one event. This reduces the overhead and keeps gas costs down. Emit fewer but more detailed events.

(2) Off-Chain Logging: For more detailed data, use off-chain solutions. While on-chain events log key contract actions, off-chain services can store and track more data. You can use oracles like Chainlink to send contract data to an off-chain service, such as IPFS or a cloud database like Firebase. This keeps on-chain events minimal and gas costs low.

(3) Use The Graph for Indexing: The Graph can help index events for easier querying. Create custom subgraphs to filter and query events with specific parameters. For deeper contract state tracking, you could query the contract at regular intervals and log this data off-chain.

(4) Gas Efficiency: On Layer 2, gas costs can still add up. To reduce costs, compress event data and limit how often state updates are logged. This approach balances the need for data with efficiency.

Would you consider using off-chain tools to complement your on-chain logs? If you do, I can suggest specific tools based on your project’s needs.

Yes, specific recommendations for off-chain tools would be very helpful.

In our Layer 2 project, we manage multiple smart contracts with high-frequency transactions. Real-time monitoring helps us quickly identify and resolve any issues, and detailed post-deployment analysis shows us how users interact with the contracts. Off-chain solutions will give us more detailed insights without adding load to the Layer 2 network.

Thank you in advance for any suggestions!

For off-chain logging and monitoring with Solidity on Layer 2, a few specific tools can handle high-frequency transactions and post-deployment analysis effectively.

(1) The Graph: Use The Graph to create subgraphs that index specific contract events. Custom subgraphs let you query and filter events based on parameters like transaction type or user address. This setup helps capture both frequent interactions and detailed user data.

(2) Chainlink Oracles: Chainlink allows your contracts to send selected event data to off-chain storage systems, like Firebase, AWS, or IPFS. This approach keeps essential information off-chain, reducing data load while allowing you to monitor key state changes.

(3) OpenZeppelin Defender: OpenZeppelin Defender provides tools for automated monitoring of smart contract activity. You can set up alerts for specific events and receive real-time notifications, which is useful for tracking high-frequency transactions. Defender also includes a dashboard for viewing contract activity.

These tools, used together, balance on-chain efficiency with comprehensive analysis. The Graph manages event indexing and querying, Chainlink stores historical data off-chain, and OpenZeppelin Defender provides active, real-time monitoring. This combination allows detailed monitoring while maintaining Layer 2 network performance.

Please feel free to ask more help. Happy coding and endless blocks of success ahead!

For frequently asked Solidity Interview questions, read our blog https://artofblockchain.club/article/top-30-interview-questions-for-senior-solidity-developers-in-2025

All these are super valuable advices.