Fintech requires full-stack engineers who understand financial correctness at every layer.
We build full-stack fintech products — the frontend, the transaction API, the ledger data model, and the compliance infrastructure required to handle money correctly. Fixed scope, fixed price.
Financial software has no tolerance for race conditions, missing idempotency, or audit trail gaps. You need a full-stack team that's shipped financial products before and knows where the edge cases are before they're discovered in production.
Financial software engineering is a specialisation, not just a category. The patterns that are acceptable in a SaaS product — optimistic UI updates, eventual consistency, background job processing without guaranteed delivery — are not acceptable in software that moves money. Every transaction needs to be atomic. Every state transition needs to be idempotent. Every financial event needs an immutable audit record. These are engineering constraints that need to be understood before the data model is designed, not applied as a patch after the first production incident.
Fintech founders often discover this the hard way: the initial build (sometimes built by generalist developers) handles the happy path correctly and fails on the edge cases that occur in production — duplicate transaction submissions, payment webhooks arriving out of order, refunds for orders that were already partially refunded. Fixing those edge cases in a production system that's processing real money is expensive, stressful, and damaging to customer trust.
The right fintech team starts with the data model. The ledger schema, the transaction state machine, the idempotency key design, and the webhook processing architecture need to be correct before the first user interface element is built. These are foundational decisions that the rest of the system is built on.
A complete, full-stack fintech product — React frontend, transaction API with idempotency, double-entry ledger, KYC integration, and HIPAA or SOC 2 ready infrastructure — built with the correctness financial software demands.
React/Next.js financial dashboard frontend
Account overview, transaction history with filtering and export, balance display with pending transactions, payment initiation flow, and statement generation. Real-time balance updates via WebSocket or polling.
Transaction API with idempotency
REST or tRPC API with idempotency key enforcement. Transaction submission, status check, and cancellation endpoints. All financial mutations wrapped in database transactions. Input validation for financial amounts (no floating point — decimal precision throughout).
Double-entry ledger data model
Account table with balance tracking. Transaction table with debit and credit entries per transaction. Atomic balance updates. Ledger reconciliation view. Journal entry history for every balance movement.
KYC/AML integration
Persona or Alloy for identity verification and watchlist screening. Customer risk tier assignment. Transaction monitoring rules. SAR case management workflow.
Compliance infrastructure
Immutable event log for all financial actions. Role-based access with audit log on every PHI or financial data access. Separate compliance report exports. Support for SOC 2 audit trail requirements. Built on Next.js, TypeScript, Postgres (decimal data types throughout), Persona for KYC, and your payment rail of choice.
One honest number to start.
Fixed-scope, fixed-price. The number below is the starting point — final scope is built from your brief.
A complete, full-stack fintech product — React frontend, transaction API with idempotency, double-entry ledger, KYC integration, and HIPAA or SOC 2 ready infrastructure — built with the correctness financial software demands.
Three steps, every time.
The same repeatable engagement on every project. No surprises, no mystery, no billable ambiguity.
Brief & discovery.
We send you questions, then get on a call. Output: a written scope with every step, feature, and integration listed.
Build & ship.
Fixed schedule, weekly reviews. No scope creep unless you change the scope — and if you do, we reprice it transparently.
Warranty & retainer.
30-day warranty on every launch. Most clients stay on a monthly retainer for ongoing features and maintenance.
Why Fixed-Price Matters Here
Fintech founders are often in conversations with banking partners or investors where the technology architecture is scrutinised. A defined scope with a defined cost demonstrates financial discipline at the company level — the same discipline you expect from the software at the transaction level.
Related engagements.
Fintech products need custom software. Compliance requirements make off-the-shelf impossible.
Read more02Your API is your product. Build it like money moves through it — because it does.
Read more03Fintech SaaS is regulated, audited, and judged in seconds. Build to those standards from day one.
Read moreQuestions, answered.
All financial amounts are stored and processed as integers (cents, not dollars) or as Postgres DECIMAL types, never as IEEE 754 floating point. Calculation is done in integer arithmetic. Display formatting is applied at the presentation layer. No floating-point arithmetic appears in the financial calculation path.
Each payment submission from the client includes a client-generated idempotency key (UUID). The API checks for the key's presence in a processed-keys table before processing. If present, it returns the cached result. If not, it processes and persists the result atomically. This prevents double-charging on network retries.
We've built integrations with Stripe, Modern Treasury, Dwolla, and Plaid. Synapse, Unit, and Bond integrations are in scope for products using those BaaS providers. The payment rail integration is the most variable part of the fintech scope; we assess the specific integration requirements in discovery.
Dashboard frontend, transaction API, ledger model, KYC integration, and compliance infrastructure typically runs $50k–$110k. Multi-currency, multi-rail, and complex transaction types add scope. Fixed-price.
14 to 20 weeks for a production-ready fintech product with correct financial infrastructure.
Tell Ryel about your project.
Describe what you’re building and what outcome you need. You’ll have a written, fixed-price scope within the week.