Technical interview guide

Blockchain & Distributed Ledger Fundamentals

What a blockchain actually is — a replicated, append-only ledger, and why that structure trades off against a conventional database.

Read: 45 min
Practice MCQs: 25
Interview QA: 25
Edition: v3
Editorial status: Reviewed
Relevant for: Blockchain Developer

Scope: NISTIR 8202; Bitcoin white paper; Ethereum developer documentation and proof-of-stake behavior reviewed 2026-09-04; Hyperledger Fabric latest documentation; IPFS documentation reviewed 2026-09-04.

Interview QA

Treat each question like a live interview question: answer out loud first (structure, assumptions, tradeoffs), then open the model answer to spot gaps and rehearse a tighter follow-up.

Curated: 2026-10-05 · Written: 2026-09-09 · Reviewed: 2026-10-03

QA-1

Explain tamper evidence and the limits of blockchain immutability.

QA-2

Design transaction authorization beyond signature verification.

QA-3

Compare UTXO and account-based ledger models.

QA-4

Handle concurrent Ethereum transaction submission from one account.

QA-5

Compare full, archive, light-client, RPC-provider, and wallet responsibilities.

QA-6

Choose between permissionless and permissioned ledger designs.

QA-7

Set a transaction finality policy for a product.

QA-8

Explain Ethereum head, justified, and finalized states to an integrator.

QA-9

Make an event indexer safe under chain reorganizations.

QA-10

Plan a production integration through a network upgrade.

QA-11

Explain gas limit, fee estimation, and reverted execution.

QA-12

Explain how nodes validate an execution payload.

QA-13

Design a ledger-backed materialized view.

QA-14

Design off-chain document anchoring with content IDs and a ledger.

QA-15

Evaluate storing personal data on-chain.

QA-16

Design an oracle-dependent contract safely.

QA-17

Explain smart-contract benefits and operational risks.

QA-18

Design application handling for failed blockchain transactions.

QA-19

Make a blockchain payment workflow idempotent.

QA-20

Run a blockchain-versus-database architecture decision.

QA-21

Critique the claim that a blockchain removes trust.

QA-22

Define identity and versioning for a blockchain integration.

QA-23

Design a reliable blockchain event consumer.

QA-24

Choose a consensus fault model for a consortium ledger.

QA-25