Technical interview guide

Layer 2 Scaling & Rollups

How rollups and other Layer 2 systems scale transaction throughput while still inheriting the base chain's security guarantees.

Read: 47 min
Practice MCQs: 25
Interview QA: 25
Edition: v3
Editorial status: Reviewed
Relevant for: Blockchain Developer

Scope: Ethereum rollup architecture and EIP-4844; OP Stack derivation, deposits, withdrawals, fault proofs and interoperability specifications reviewed 2026-09-04; Arbitrum Nitro architecture (protocol-specific parameters must be verified at deployment).

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: 2026-10-05 · Reviewed: 2026-10-03

QA-1

Define the trust boundary of a proposed rollup.

QA-2

Validate state commitments in a rollup node.

QA-3

Threat-model a fault-proof game.

QA-4

Specify an assertion lifecycle.

QA-5

Design a confirmation model for an L2 wallet.

QA-6

Explain and operate an optimistic withdrawal.

QA-7

Review a validity-rollup proving pipeline.

QA-8

Define a rollup data-availability strategy.

QA-9

Operate batch publication with blobs.

QA-10

Implement and test a derivation pipeline.

QA-11

Set confirmation thresholds for an exchange deposit.

QA-12

Test rollup behavior across L1 reorgs.

QA-13

Evaluate a rollup's censorship escape path.

QA-14

Design around sequencer failure.

QA-15

Integrate canonical deposits safely.

QA-16

Implement a withdrawal finalizer.

QA-17

Compare canonical and fast bridge routes.

QA-18

Secure a cross-domain admin message.

QA-19

Design an asynchronous cross-rollup workflow.

QA-20

Build an honest L2 fee estimator.

QA-21

Port an Ethereum application to an EVM-like rollup.

QA-22

Assess rollup governance and upgrade risk.

QA-23

Set safety rules for cross-rollup messages.

QA-24

Compare centralized proving against decentralized prover marketplaces for a ZK-rollup in terms of latency, unit economics, hardware requirements, and failure modes.

QA-25