Consensus and Scalability Innovations BDC Practice Questions (Page 5)

Questions 21–25

1. 21application · medium

   A bank is deploying a permissioned blockchain with 20 nodes. They need to tolerate up to 6 faulty nodes and still reach consensus. Which consensus mechanism should they choose?

   • ADPoS, because it uses a small set of delegates and can tolerate many faulty nodes.
   • BDAG-based consensus, because it can tolerate any number of faulty nodes.
   • CPBFT, because it can tolerate f faulty nodes as long as the total number of nodes n satisfies n > 3f.
   • DPoW, because it is the most secure and can tolerate any number of faulty nodes.
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2. 22foundation · easy

   What is a key advantage of Practical Byzantine Fault Tolerance (PBFT) over Proof of Work?

   • AIt provides finality without the need for probabilistic confirmations
   • BIt can achieve consensus without a central authority
   • CIt requires no energy consumption at all
   • DIt does not require any communication between nodes
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4. 23application · medium

   A consortium of banks is building a permissioned blockchain for interbank payments. They need to process thousands of transactions per second and have a fixed set of known member nodes. They are considering sharding to improve throughput. Which approach best fits their environment?

   • AImplement sharding with a small number of shards, each processing a subset of accounts, and use a beacon chain to coordinate cross-shard transactions.
   • BAdopt a DAG-based structure instead, because sharding is only applicable to public blockchains.
   • CUse a single shard for all transactions to avoid cross-shard complexity, since the consortium is small.
   • DRely on a Layer 2 state channel network to handle all interbank payments off-chain.
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5. 24expert · hard

   A public blockchain is implementing sharding to increase throughput. They need to ensure that cross-shard transactions are atomic and that the network remains secure against a malicious actor controlling a single shard. Which design consideration is most critical?

   • AUsing a beacon chain to coordinate cross-shard transactions and randomly assigning validators to shards to prevent shard takeover.
   • BImplementing sharding only for read operations, while keeping all writes on the main chain.
   • CUsing a fixed set of validators for each shard to ensure stability.
   • DAllowing each shard to have its own consensus and no cross-shard communication to maximize parallelism.
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6. 25application · medium

   An IoT company is evaluating a blockchain for recording sensor data from millions of devices. They need high write throughput and low latency, and they are willing to accept probabilistic finality. Which architecture should they consider?

   • AA PBFT-based permissioned chain with a small validator set and immediate finality.
   • BA traditional linear blockchain with a single block producer to keep ordering simple.
   • CA DAG-based ledger where each new transaction references and validates previous transactions, allowing parallel processing.
   • DA Layer 2 state channel network that requires all devices to be online and lock funds.
   Reveal Solution Discussion Select an answer first