Deploy and Manage dApps BDC Practice Questions (Page 1)

Questions 1–5

1. 1expert · hard

   A dApp's backend is missing some contract events, but the frontend shows no errors. The backend uses a WebSocket connection to an RPC provider. Which troubleshooting step is most likely to identify the root cause?

   • AVerify that the contract address in the backend configuration matches the deployed contract.
   • BCheck the WebSocket connection's reconnection logic and the block range used for event queries.
   • CIncrease the backend's logging level to debug and restart the service.
   • DSwitch from WebSocket to HTTP polling with a shorter interval.
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2. 2expert · hard

   A team manages a dApp with a multi-sig wallet as the owner of the upgradeable contract. They need to perform an upgrade, but the multi-sig requires 3 of 5 signatures. One team member is on vacation and cannot sign. The upgrade is time-sensitive. What should they do?

   • ADeploy a new contract and migrate users to it, bypassing the upgrade.
   • BTemporarily change the multi-sig to require only 2 signatures, execute the upgrade, then change it back.
   • CWait for the team member to return and then execute the upgrade.
   • DUse the admin key to directly upgrade the contract without the multi-sig.
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4. 3expert · hard

   A dApp is running on a private blockchain network that is being decommissioned. The team needs to migrate the dApp to a public testnet. The smart contract holds user balances and other critical state. What is the most important step in the migration plan?

   • AExport the contract's state and replay all transactions on the new network.
   • BSnapshot the old contract's storage and manually insert it into the new contract's storage.
   • CCreate a migration contract that reads the old contract's state and writes it to the new contract.
   • DDeploy a new contract on the testnet and have users manually transfer their balances.
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5. 4application · medium

   A developer is deploying a dApp to the Sepolia testnet. The frontend is a React app that will be hosted on a static web server, and the smart contract is written in Solidity. The developer has already compiled the contract and has the ABI and bytecode. Which additional step is REQUIRED before the frontend can interact with the deployed contract?

   • AAdd the contract's source code to the frontend's public folder so the browser can compile it.
   • BRun a local Ganache instance and deploy the contract there, then configure the frontend to use the local network.
   • CDeploy the contract using a script that sends a signed transaction to Sepolia and then update the frontend's configuration with the contract address and ABI.
   • DUpload the compiled bytecode to a centralized server so the frontend can reference it at runtime.
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6. 5foundation · easy

   Which tool is commonly used to aggregate and visualize logs from a dApp's backend services?

   • AA wallet like MetaMask
   • BA block explorer like Etherscan
   • CA log management platform like the ELK stack (Elasticsearch, Logstash, Kibana)
   • DA smart contract compiler like Solc
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