Design Crypto KYC System - System Design | WinJob

Problem Statement: Crypto KYC and Identity Verification

Design a Chainalysis-adjacent compliance stack with Jumio/Onfido-class identity verification for crypto exchanges and wallets: capture documents, score risk, screen sanctions, issue tier credentials, and prove every decision to regulators. This section focuses on problem during the understanding phase.

Mechanism

Retail and institutional users submit government ID, selfie, and proof-of-address before trading or withdrawing
Orchestrator routes cases to Jumio/Onfido-class vendors with fallback when SLA breaches
Risk engine assigns tier (basic, enhanced, EDD) that gates fiat ramps and withdrawal limits
Immutable audit trail links every decision to vendor payload hash and analyst action

Quantified anchors

Target: 2M verified users, 40k new onboarding sessions/day
p99 case decision < 90s for auto-approved low-risk retail

Failure drills (problem)

Treating vendor webhook as source of truth without internal case state machine
Storing passport images in application logs

Staff+ extensions

Tie controls to FinCEN MSB / EU MiCA audit evidence and SOC2 CC6/CC7
Document failover drills for vendor degradation and region loss

Invariants for crypto KYC

Case invariant: internal case service is CP; vendor dashboards are projections only
PII invariant: documents live in encrypted object store; APIs return references not raw images
Tier invariant: exchanges enforce limits from signed credentials, never from vendor emails

Interview checkpoints

Separate KYC platform from exchange matching in one sentence
Name actors: applicant, compliance analyst, vendor, downstream product (exchange/wallet)

Depth note A.1: Retail and institutional users submit government ID, selfie, and proof-of-address before trading or withdrawing — measured by Target: 2M verified users, 40k new onboarding sessions/day while executing problem for crypto KYC.

Depth note B.2: Orchestrator routes cases to Jumio/Onfido-class vendors with fallback when SLA breaches — measured by p99 case decision < 90s for auto-approved low-risk retail while executing problem for crypto KYC.

Depth note C.3: Risk engine assigns tier (basic, enhanced, EDD) that gates fiat ramps and withdrawal limits — measured by Target: 2M verified users, 40k new onboarding sessions/day while executing problem for crypto KYC.

Depth note D.4: Immutable audit trail links every decision to vendor payload hash and analyst action — measured by p99 case decision < 90s for auto-approved low-risk retail while executing problem for crypto KYC.

Depth note E.5: Retail and institutional users submit government ID, selfie, and proof-of-address before trading or withdrawing — measured by Target: 2M verified users, 40k new onboarding sessions/day while executing problem for crypto KYC.

Depth note F.6: Orchestrator routes cases to Jumio/Onfido-class vendors with fallback when SLA breaches — measured by p99 case decision < 90s for auto-approved low-risk retail while executing problem for crypto KYC.

javaOne Dark Pro

1 public final class problemPolicyGate {
2   public boolean allow(KycCase c, RiskPolicy p) {
3     return c.riskScore() < p.autoApproveMax()
4         && !c.sanctionsHit() && c.vendorStatus() == VendorStatus.CLEAR;
5   }
6 }

pythonOne Dark Pro

1 @dataclass(frozen=True)
2 class problemMovement:
3     tenant_id: str
4     case_id: str
5     idempotency_key: str
6     jurisdiction: str

typescriptOne Dark Pro

1 export function kycIdempotencyKey(tenant: string, clientRef: string): string {
2   return `kyc:${tenant}:${clientRef}`;
3 }

Why interviewers care

Crypto KYC System interviews reward crisp scope, explicit trade-offs, and failure stories—not generic microservice diagrams.

Interview checkpoint

Name one failure story for Problem Statement: Crypto KYC and Identity Verification that proves you understand real outages, not happy-path diagrams.

Key Highlights

•Retail and institutional users submit government ID, selfie, and proof-of-address before trading or withdrawing.
•Orchestrator routes cases to Jumio/Onfido-class vendors with fallback when SLA breaches
•Risk engine assigns tier (basic, enhanced, EDD) that gates fiat ramps and withdrawal limits
•Immutable audit trail links every decision to vendor payload hash and analyst action

1	public final class problemPolicyGate {
2	public boolean allow(KycCase c, RiskPolicy p) {
3	return c.riskScore() < p.autoApproveMax()
4	&& !c.sanctionsHit() && c.vendorStatus() == VendorStatus.CLEAR;
5	}
6	}

1	@dataclass(frozen=True)
2	class problemMovement:
3	tenant_id: str
4	case_id: str
5	idempotency_key: str
6	jurisdiction: str

1	export function kycIdempotencyKey(tenant: string, clientRef: string): string {
2	return `kyc:${tenant}:${clientRef}`;
3	}