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/ Sector playbook

Fintech & Payments

Ledgers that balance, regulators that approve.

We design idempotent ledgers, KYC/AML flows and payment rails that survive audit — built by engineers who've shipped to regulated production.

Fintech is the one domain where a single bug can cost the company. We design the system around that fact: every monetary event is recorded as an immutable double-entry journal, every external call is idempotent, every state change is auditable.

We default to a clear separation between the regulated entity and the application. KYC/AML, sanctions screening and transaction monitoring sit in their own service with their own audit log. Compliance can review without grepping the app.

On the customer side, we obsess over the boring details — clear receipts, accurate disclosures, fraud disputes that resolve in days not weeks. Trust is the product.

/ Common challenges

What founders bring us

Regulatory licensing scope unclear (MSB, EMI, broker-dealer, etc.)
Ledger design errors discovered too late
KYC/AML provider lock-in or false-positive rates
Reconciliation breaks between ledger, processor and bank
Fraud + chargeback economics killing the take rate

/ Our approach

How we build it

01

Double-entry ledger

Immutable journal, signed entries, period-close runs and reconciliation reports built-in.

02

Idempotent everywhere

Every API and webhook handler safe to replay. No duplicate charges, ever.

03

Compliance-first

KYC, AML, sanctions, transaction monitoring as a separate, audit-friendly service.

04

Explainable fraud

Rules engine with traceable decisions; human-in-the-loop for edge cases.

/ Tech stack

Tools we reach for

Core
  • Postgres ledger
  • Idempotency keys
  • Outbox pattern
  • Event log
Payments
  • Stripe / Adyen / direct rails
  • Card + ACH + SEPA
  • Open Banking
  • FX & multi-currency
Compliance
  • KYC / KYB providers
  • Sanctions screening
  • Transaction monitoring
  • Audit trail
Security
  • HSM-backed keys
  • PCI scope minimization
  • RBAC + MFA
  • Pen-test ready

/ Typical timeline

From idea to live

  1. Phase 01
    Idea & plan
    2–3 wks

    Regulatory scoping, ledger design, license strategy

  2. Phase 02
    Build
    10–16 wks

    Ledger, KYC, payments, dashboard, compliance ops

  3. Phase 03
    Launch
    3–4 wks

    Closed pilot, bank/regulator review, gradual rollout

  4. Phase 04
    Grow
    Ongoing

    Volume scaling, fraud tuning, new corridors / products

/ Mini case study

Real outcomes

Cross-border payments

Prylink

Problem

Launch a remittance corridor in under 3 months with full compliance posture.

Solution

Built double-entry ledger, KYC + sanctions in a separate service, T+0 settlement on first corridor.

Volume / mo
$1.2M
Settlement
T+0
Take rate
1.4%

/ Regulatory & compliance notes

What the regulator expects

Fintech is a regulated industry first and a software product second. We design the controls before we write the features — because retrofitting them after launch costs the company.

PCI-DSS (L1–L4)

Tokenized card capture, network segmentation, quarterly ASV scans, full audit log of cardholder-data access.

KYC / AML / CFT

BSA / FinCEN (US), MLR 2017 (UK), AMLD6 (EU): identity + sanctions screening, SAR workflow, 5-year record retention.

PSD2 / SCA

Strong customer authentication, 3-D Secure 2, dynamic linking on payment initiation for EU / UK rails.

SOC2 + ISO 27001

Security, availability and confidentiality controls plus formal ISMS — both expected by bank partners.

Licensing posture

MSB / EMI / broker-dealer scoping done up front — built as licensee or under a sponsor bank, never accidentally.

  • Double-entry ledger is immutable and signed; period-close reports generated automatically.
  • Sanctions list (OFAC, UN, EU, UK HMT) refreshed daily with delta alerts to compliance.
  • Suspicious-activity workflow with 4-eyes review and regulator-export format built in.

Informational only — not legal advice. Final scope is confirmed with your counsel and regulator of record.

/ Frequently asked

Fintech & Payments — common questions

Q01Do we need a banking license to launch?

Often no — many products launch under a sponsor bank or a licensed BaaS partner while preparing their own EMI / MSB / e-money licence in parallel. We scope this in week one with your counsel.

Learn more · How we build it
Q02How do you prevent double-charges and lost transactions?

Idempotency keys on every API and webhook, a double-entry immutable ledger, an outbox for downstream events and reconciliation jobs against the processor and bank. Replays are safe by construction.

Learn more · Tools we reach for
Q03Which KYC / AML providers do you integrate?

Persona, Onfido, Sumsub, Alloy and ComplyAdvantage are the most common. We isolate the provider behind an internal interface so you can switch without touching product code.

Learn more · Typical timeline
Q04Can you ship to multiple jurisdictions?

Yes — multi-currency, FX, per-country KYC rules, sanctions lists (OFAC/UN/EU/UK HMT), data residency and per-jurisdiction reporting are all first-class concerns in the architecture.

Learn more · See a real outcome

/ Outcomes you can expect

What you walk away with

  • Zero financial discrepancies across reconciliation runs
  • Audit-ready ledger from day one
  • Compliance review passed on first submission (typical)
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