Design Name Service - System Design | WinJob

Problem Statement: Ethereum Name Service

ENS maps human-readable names (e.g., alice.eth) to machine identifiers—primarily Ethereum addresses, but also IPFS content hashes, text records, and DNS-imported zones. The registry is a Merkleized tree keyed by namehash; resolvers are pluggable contracts per node.

Mechanism (sec-01)

Wallet interacts with Gateway under namehash invariants
Registry emits events consumed by Resolver projections
L1 remains consistent within one finalized block window

ENS invariants

The registry owner field and resolver address at a node are authoritative on-chain at block B. Gateway caches are hints keyed by (namehash, blockTag) and must invalidate on NewResolver or Transfer events.

Failure modes (problem)

stale Resolver after reorg depth > confirmation threshold
Wallet hotspot during NFT-style label drop
Registry outage forcing wallets to raw RPC (latency spike)

Interview checkpoint (sec-01)

Quote namehash, commit-reveal, grace period, and CCIP-Read when understanding interviewers press ENS specifics—not generic DNS slides.

Staff+ talking point

Separate forward (name→address) from reverse (address→primary name). Wallets that skip reverse still work, but explorers and reputation systems need both.

Deep dive (problem)

For Problem Statement: Ethereum Name Service, explain how Wallet, Gateway, Registry, Resolver, L1 cooperate under load. Mention EIP-137 resolution, ENSIP-10 wildcard resolvers, and gasless reads via gateway with Merkle proofs where applicable. Close with a concrete story: user renews brand.eth late, enters grace, competitor attempts register—walk timeline with on-chain events.

javaOne Dark Pro

1 public final class EnsSection1 {
2   public static final String TOPIC = "problem";
3   public static byte[] namehash(String name) { return new byte[32]; /* keccak iterative */ }
4 }

pythonOne Dark Pro

1 SECTION_1_TOPIC = "problem"
2 GRACE_PERIOD_DAYS = 90
3 def is_available(expiry_ts: int, now: int) -> bool:
4     return now > expiry_ts + GRACE_PERIOD_DAYS * 86400

typescriptOne Dark Pro

1 export const SECTION_1 = { topic: 'problem', phase: 'understanding' } as const;
2 export function cacheKey(namehash: string, blockTag: number | 'latest'): string {
3   return namehash + ':' + String(blockTag);
4 }

Why interviewers care

Name Service interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Ethereum Name Service that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Wallet ↔ Gateway boundary
•Registry projections with block tags
•Phase understanding: problem focus

1	public final class EnsSection1 {
2	public static final String TOPIC = "problem";
3	public static byte[] namehash(String name) { return new byte[32]; /* keccak iterative */ }
4	}

1	SECTION_1_TOPIC = "problem"
2	GRACE_PERIOD_DAYS = 90
3	def is_available(expiry_ts: int, now: int) -> bool:
4	return now > expiry_ts + GRACE_PERIOD_DAYS * 86400

1	export const SECTION_1 = { topic: 'problem', phase: 'understanding' } as const;
2	export function cacheKey(namehash: string, blockTag: number \| 'latest'): string {
3	return namehash + ':' + String(blockTag);
4	}