Custom Software for Fintech — Built Compliant, Built Secure, Built to Ship

PCI-DSS scope, SOC 2 Type II, SOX 404 for public-company affiliates, KYC and AML obligations on every onboarded customer, GLBA on customer data, state-level money transmission rules depending on the model — fintech is one of the most regulated software environments outside of healthcare. Off-the-shelf SaaS will not pass your auditor. A code base built by a contractor who has never read a SAQ will not either.

We build with those frameworks in mind from the first architecture diagram. Card data is tokenized at the edge — Stripe Elements or Checkout — so your environment stays in SAQ A. PII gets encrypted at rest with envelope keys and in transit with TLS 1.3. Role-based access is wired through every admin surface, and the audit log is immutable by design so your SOC 2 auditor has something real to look at.

Most industries deal with one or two overlapping frameworks. Fintech routinely sits at the intersection of five or six. A single advisor CRM that bills a recurring fee through Stripe, ingests client investment positions from a custodian feed, and notifies a producer of a suitability change can simultaneously touch PCI-DSS scope, SOC 2 trust criteria, GLBA Safeguards Rule obligations, and broker-dealer recordkeeping under FINRA 17a-4. That is before you get to state-level money-transmission rules if you move customer funds.

Scale compounds the problem. The volume of customer records, transactions, and audit-relevant events in even a small fintech is large enough that lazy logging or untested encryption becomes a liability inside a quarter. And the integrations are intricate: Plaid for account aggregation, Stripe Connect for payouts, broker APIs like Interactive Brokers or Alpaca, KYC vendors like Persona or Alloy, sanctions screeners, transaction-monitoring engines, and a clearing or BaaS layer underneath. Each one has its own quirks, its own rate limits, its own retry semantics, and its own failure modes when something goes wrong at 2 a.m. We have wired this stack repeatedly and know where the time gets eaten on a build.

PCI-DSS. If you take card payments, you are in PCI scope. Our default architecture tokenizes card data with Stripe Elements or Checkout so you live in SAQ A — the lightest validation level. For Stripe Connect platforms collecting card data directly, we work with your QSA to scope SAQ A-EP or SAQ D-Merchant honestly and document the boundary.

SOC 2 Type II. Most enterprise buyers will not even take a meeting without your SOC 2 report. We build with Common Criteria mapped to controls: encryption at rest and in transit, RBAC, change management, immutable audit logging, incident response, vendor management, and access reviews. We can produce evidence packs for Vanta, Drata, or Secureframe in the format your auditor expects.

SOX 404. When your fintech feeds the financial reporting of a public company — directly or via material affiliate — ICFR controls apply. We handle segregation of duties, deployment approvals, and change traceability so your SOX testing does not turn into a fire drill.

KYC, AML, and BSA. Identity verification, sanctions screening, PEP screening, transaction monitoring, and SAR workflows are wired through dedicated vendors (Persona, Alloy, ComplyAdvantage, Sardine). We never roll our own identity verification — the false-positive economics are brutal and the regulatory standard is moving.

GLBA Safeguards Rule. The 2023 FTC amendments brought non-bank financial institutions into a much sharper regime: written information security program, named CISO, board reporting, MFA, encryption, incident response, and annual testing. Our builds align by default; we coordinate with your CISO or compliance officer on the formal program documentation.

State money transmission and consumer-protection statutes. Reg E, Reg Z, Reg DD, NMLS where applicable, and state-by-state MTL obligations vary widely. We do not give legal advice — but we build the audit trail, disclosure capture, and consent-flow logging that your counsel will need to defend the product.

Next.js 15 or 16 on the App Router with React 19 and TypeScript end-to-end. Postgres for the system of record — usually Neon, Supabase, or RDS depending on the compliance posture and BAA needs. Prisma or Drizzle as the type-safe ORM. Stripe for cards and Connect payouts. Plaid for account aggregation when needed. Resend for transactional email with a verified domain and DMARC alignment. Sentry plus a log aggregator (Datadog or Better Stack) for observability — PHI- and PII-aware redaction baked into the logger.

For trading and execution we lean Python on the engine side, with FastAPI or a private gRPC layer between the strategy worker and the broker adapter. A Node or TypeScript dashboard sits over the top for human review. Background workers run on Inngest or a self-hosted queue (BullMQ on Redis) depending on the SLA. Auth0, Clerk, or a Lucia-style stack for authentication; we wire MFA-required everywhere on admin and producer surfaces. KMS-backed envelope encryption for sensitive columns; signed audit logs in a separate append-only store. Deployment goes to Vercel for the web tier and to a hardened VPC for the data plane when SOC 2 or BAA scope requires it.

Three patterns repeat. First, founders push a fintech product live without an immutable audit log and discover during the first SOC 2 readiness assessment that they cannot reconstruct who-did-what on customer money. Rebuilding the audit layer after the fact means re-instrumenting every write path. Build the audit log first, not last.

Second, KYC gets implemented as a one-shot signup gate instead of an ongoing program. The first time a sanctions list updates and someone in your existing customer base is suddenly a hit, the company learns it has no rescreening process and no SAR workflow. Identity verification at onboarding is the easy 30%. Ongoing monitoring, escalation, and recordkeeping are the part that actually keeps the company out of trouble.

Third, teams overscope the first release. A new fintech product gets pitched with five integrations, three customer personas, two pricing models, and a road map of regulatory states. The realistic build is one persona, one pricing model, and one state — shipped in eight weeks, used by ten beta users, and learned from. We push hard for that scoping discipline because the alternative is a 9-month build that ships a year late and serves no one.

The thing that gets fintech founders in trouble is not usually a bug. It is the laptop in another country with your trading logic on it, or the contractor who copied your customer database before the engagement ended. IP exfiltration is the quiet existential risk in fintech engineering — and it is precisely why we are US-based, founder-led, and engagement-first on every project.

William Beltz writes or reviews every line of code that touches your customers, your money flows, or your trading logic. NDAs are mutual and signed before discovery. Source code lives in your GitHub organization, not ours. The handoff is documented for either ongoing collaboration or in-house ownership — your call.

Auditors and cyber-insurance carriers increasingly want pentest reports mapped to the techniques your industry's actual adversaries use — FIN7 for card-data theft, APT38 and Lazarus for crypto and SWIFT, ransomware affiliates for everyone. We run MITRE ATT&CK-aligned assessments that simulate those groups' documented TTPs against your environment, then deliver an ATT&CK heatmap of which techniques succeed, which get detected, and which get blocked.

Standard penetration testing covers the rest — internal network, Active Directory, external perimeter, web app, and API surface. Every finding maps to ATT&CK technique IDs so your SOC or MSSP knows what to alert on. See the Active Directory pentest case study for the reference engagement structure.

J5 Sales OS is the architecture pattern we use for prospecting and pipeline platforms in financial services — Google Places discovery, concurrent email enrichment, OpenAI qualification, and a full CRM pipeline in one tool. The same patterns power custom advisory CRMs and marketplace operator dashboards.

ProtectWithBri is our reference for personal-advisor digital presence — a personal-insurance practice that needed a high-trust, high-conversion site that captured qualified consultation requests. Same architecture works for RIA practice sites and fee-only advisor pages.

For execution-side fintech, see the multi-strategy trading system deployment — Python execution engine, exchange WebSocket feeds, hard risk controls, and a Node dashboard, with sub-12ms order latency and zero unplanned downtime since launch.