Bitcoin and Bitcoin Blockchain Architecture BDC Practice Questions (Page 3)

Questions 11–15

1. 11expert · hard

   A company is deciding whether to run a full node or use a lightweight client for its Bitcoin payment processing. The company needs to verify transactions independently and ensure no invalid transactions are accepted. Which choice best meets this requirement, and what is the trade-off?

   • AUse a third-party API; it provides validated transaction data without the need to run any node.
   • BUse a lightweight client; it is fast and low-cost, and it can verify transactions using Merkle proofs.
   • CRun a mining node; it provides the same validation as a full node and also earns block rewards.
   • DRun a full node; it validates all transactions and blocks against consensus rules, but requires significant storage and bandwidth.
   Reveal Solution Discussion Select an answer first
2. 12expert · hard

   A developer is part of a team proposing a Bitcoin upgrade that would reduce the block size limit from 1 MB to 500 KB. The team wants to avoid a network split. Which type of fork should they implement?

   • AA hard fork, but only if all nodes upgrade simultaneously
   • BA hard fork, because the change is too significant to be backward-compatible
   • CA soft fork, because the new rule is more restrictive and old nodes will still accept the new blocks
   • DA soft fork, but only if the majority of miners signal support
   Reveal Solution Discussion Select an answer first
4. 13expert · hard

   A developer is debugging a transaction that fails to broadcast. The transaction spends a UTXO that was created in a block that is now orphaned. What is the most likely reason the transaction is invalid?

   • AThe UTXO no longer exists in the UTXO set because the block was reorganized out of the chain
   • BThe transaction fee is too low
   • CThe transaction's signature is invalid
   • DThe transaction's locktime has not expired
   Reveal Solution Discussion Select an answer first
5. 14application · medium

   A developer is implementing a Merkle tree for a block with exactly 5 transactions. The developer hashes each transaction and then pairs them to build the tree. What is the correct approach to handle the odd number of leaves?

   • ADiscard the last transaction and build the tree from the first four.
   • BDuplicate the last transaction's hash and hash it with itself to create a balanced tree.
   • CUse the last transaction's hash as the root directly, skipping the remaining levels.
   • DAdd a dummy transaction with a zero hash to make the count even.
   Reveal Solution Discussion Select an answer first
6. 15application · medium

   A developer is building a service that monitors the Bitcoin network for double-spend attempts. Which data should the service track to detect when a UTXO is spent more than once?

   • AThe set of all unspent transaction outputs and the transactions that reference them
   • BThe block headers of all blocks in the chain
   • CThe Merkle roots of recent blocks
   • DThe difficulty adjustments over time
   Reveal Solution Discussion Select an answer first