DField SolutionsMérnöki stúdió · Budapest
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CASE STUDIES · fintech

KYC + payments re-integration for a HU fintech · MNB audit clean, 72% onboarding-time drop

A Hungarian fintech scale-up had failed two MNB mini-audits on KYC evidence chain. We rebuilt the onboarding with SumSub + SimplePay integration, risk-scoring persistence, and a proper audit-trail schema.

Timeline6 weeks
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Reviewed by
01MNB re-audit passed clean · all prior findings marked resolved.
02 / Onboarding time7m40s → 2m10s (−72%).
03 / Document-upload abandonment34% → 11%.
04 / Webhook event loss3% → 0.02% (within SumSub's published SLA).
The problem01 / 03
  • 01Two MNB findings on 'KYC result reproducibility' · couldn't rebuild a customer's risk score 6 months later.
  • 02Onboarding time averaging 7m40s · cart abandonment at document upload step was 34%.
  • 03SumSub webhooks dropped ~3% of events · some customers stuck in 'pending' forever.
  • 04Risk-scoring logic was a big if/else chain · no versioning, untestable.
The solution02 / 03
  • 01Event-sourced risk scoring · every input (doc, score, flag) is persisted with a version tag.
  • 02Webhook reconciliation loop · every 5 minutes, poll SumSub API for pending onboardings older than 10min.
  • 03SimplePay integration rebuilt with proper Idempotency-Key handling on retries.
  • 04Versioned rule engine for risk scoring · when MNB asks 'why was customer X approved in Feb', we replay against the v2.3 rules that were live then.
  • 05Audit-trail dashboard in Grafana showing end-to-end onboarding flow per customer.
The outcome03 / 03
  • 01MNB re-audit passed clean · all prior findings marked resolved.
  • 02Onboarding time: 7m40s → 2m10s (−72%).
  • 03Document-upload abandonment: 34% → 11%.
  • 04Webhook event loss: 3% → 0.02% (within SumSub's published SLA).
  • 05Risk scoring now reproducible to any point in time via event log replay.
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