FinTech Product Architecture & Engineering

Architecture & full-cycle engineering

We design and build fintech products that survive audit, load, and the first year in production.

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What it covers

System & API architecturepayments · lending · billing
Full-stack buildwe ship and own it
Cloud-nativescales with you
Secure & compliantfrom day one
Built for uptimeload-tested

Why teams bring us in

Three situations account for most of the calls we take.

The prototype hit its ceiling
Something built for a pilot now carries payment volume it was not designed to hold. Reconciliation runs overnight and still disagrees with the processor. Each new feature touches the same three files. We keep the working parts, redraw the boundaries around them, and replace what cannot carry the next two years.
Compliance arrived late
An auditor asked where card data lives and the answer took three weeks to assemble. Cardholder scope has spread across services that had no reason to see a PAN. We map the data flows, pull scope back to a tokenization boundary, and document the control evidence as part of the build rather than after it.
The team is short of fintech hands
Engineers who have shipped a ledger, handled a chargeback flow, or read an ISO 20022 message take months to hire. You do not have those months. We staff a team that has done this work before, sits inside your repo and your review process, and leaves the domain knowledge behind in code and written decisions.

Architecture and design

Design work happens before the first sprint, and it is mostly about where money and data are allowed to move.

System and API architecture

We start with money movement rather than screens. Each state a payment, loan, or invoice can occupy gets written down, together with the transitions that are legal and the ones the system must reject. That model becomes the API contract, the database schema, and the test matrix, so the three cannot quietly drift apart. Reviews happen on the model before code exists.

Compliance and security by design

Scope decisions made in month one decide the audit cost in year two. We draw the PCI DSS 4.0 boundary on the architecture diagram, keep cardholder data inside a tokenization service, and treat what sits outside that line as out of scope by construction. Consent records, audit trails, and data residency get their own storage rules, written before the first migration runs.

Cloud platform and delivery shape

Teams often inherit a platform they cannot reproduce. One engineer knows how staging was built, and nobody can stand up a clean environment. We define the infrastructure as code from the first sprint, so environments are rebuildable, and we keep the stack portable across a managed cloud, a private VPC, or hardware you own. Self-hosting stays an option rather than a rewrite.

Build and integration

Build starts once the state model and the scope boundary are agreed.

Full-stack engineering teams

The team that draws the architecture writes the code. Backend services, the web or mobile client, and the database work sit with one group, which removes the handoff where design intent goes missing. Engineers pick up tickets in your tracker, open pull requests against your repo, and take the on-call pager for what they built.

Payment and banking integrations

Processor sandboxes lie. Documentation describes the happy path, and production sends you partial captures, delayed webhooks, and settlement files that arrive in a different order than the events. We build each integration behind an internal contract, with idempotency keys on write paths and a replay log for webhooks, so a duplicate callback does not become a duplicate charge.

Ledger and reconciliation

Balances computed on the fly stop matching once refunds, fees, and currency conversion enter the picture. We put a double-entry ledger underneath. Each movement is recorded as an immutable entry, balances are derived from it, and reconciliation runs against processor and bank files on a schedule. Breaks land in a queue a finance person can work through.

Data and event backbone

Reports run against the transactional database and slow checkout down. The dashboard numbers rarely agree with the ledger. We publish domain events once, then feed the read models, the analytics warehouse, and the risk checks from that single stream. Schema versions stay explicit, so a consumer added next quarter does not break the producer.

Hardening and handover

Launch week is planned weeks earlier.

Testing and release gates

Manual regression before each release turns a two-day fix into a two-week event. We build the suite alongside the product, with contract tests against processor sandboxes, property tests on the ledger invariants, and load runs that hold the target throughput for an hour. The pipeline blocks a merge when coverage of the money paths drops.

Production readiness

A launch date settles little on its own. Two weeks before it, the same senior engineers run the failure drills, kill a processor connection, replay a webhook storm, and watch what the alerts say. Dashboards track authorization rate, settlement lag, and reconciliation breaks, and each alert links to a runbook page with the steps someone on call can follow at 3am.

Handover and ownership

Vendor exits usually leave a repo nobody understands. We work the other way. Architecture decision records, the threat model, the deployment scripts, and the audit evidence pack sit in your repository throughout the engagement. Your engineers pair on the last sprints, run a release themselves, and we stay on a reduced retainer for the first months after launch.

How we work

Four habits that decide whether the second year is cheaper than the first.

Presales engineering
Architects read the problem before anyone quotes it: what exists, what regulation applies, and where the data lives. You get a System Design and an estimate that survives contact with the estate.
Contracts before implementations
Integration points are written as API contracts first, so teams build in parallel and integration stops being the phase where the schedule dies.
Increment and harden together
Senior engineers ship in tight slices, with security, compliance and load testing inside the increment rather than queued behind it.
Run or hand over
Documented systems, the tests that prove them, and a team that could take it from here. We stay on to operate it when that is what you want.

Engagement shape
One team through architecture, build, and hardening
The engineers who draw the first diagram are the ones answering the pager in launch week.

What you get

A running product and the code behind it
Source code in your repository under your license, with commit history, review threads, and the branch strategy intact. Build and deploy pipelines come with it, so a release does not depend on a machine or a person at our end.
Architecture written down
A decision record for each significant choice, with the option that was picked, the ones rejected, and the reason. Service boundaries, data ownership, and the failure modes each service is expected to survive are documented in the same place as the code.
An audit evidence pack
Data flow diagrams, the cardholder scope boundary, key management notes, and the control mapping your assessor asks for. Penetration test findings and their fixes are tracked in the same backlog as feature work, with dates and the commit that closed each one.
A team that can run it without us
Runbooks for the on-call rotation, the reconciliation break procedure, and the rollback path. Your engineers sit in our reviews from the first sprint and drive the final releases, so the handover is a formality by the time the contract ends.

Where this works best

We would rather decline an engagement than take the wrong one.

Talk to the team who would build it

Good fit
A product that will carry money or regulated data, and a team that wants the architects who designed it to stay through production.
Not a fit
A prototype whose only requirement is to exist by Friday. We will say so in Discovery instead of billing for the wrong shape of work.

20+

Years in software engineering

300+

Engineers

50+

Clients, incl. Fortune 500

Questions

The questions procurement and engineering ask on the first call.

Where does an engagement usually start?

Most start with a two to four week architecture review. We read the code you have, talk to the people who built it, and map the money flows and the compliance scope as they stand today. The output is a target architecture, a list of the risks worth fixing first, and a build plan with a team shape and a sequence. You can take that plan elsewhere.

Do you take PCI DSS 4.0 responsibility?

We are the engineering vendor, so the certification sits with you or your acquirer. What we do is keep the scope small and the evidence current. Cardholder data stays inside a tokenized boundary, we implement the technical controls your assessor will test, and we produce the diagrams, key management notes, and change records they ask for. Your QSA runs the assessment. We answer the technical questions.

Can the product be self-hosted?

Yes. We package deployments as containers with infrastructure as code, and we avoid managed services that have no portable equivalent. The same build then runs on a public cloud account, inside your VPC, or on hardware you own. Data residency rules are a common reason clients ask, and keeping the option open costs little if it is designed in early rather than retrofitted after launch.

Who works on the project after launch?

The same engineers. The people who wrote the code handle hardening, the failure drills, and the first weeks in production, and we do not swap in a cheaper maintenance crew at go-live. After handover most clients keep a small retained team for incident support and the follow-on roadmap, sized down as their own engineers take over.

How do you work with an existing in-house team?

Our engineers join your repository, your tracker, and your review rotation. Pull requests go through your approvers, and your architects sit in the design sessions with veto rights. Where the split makes sense we take a bounded area, the ledger or the processor integrations, and your team keeps the product surface. We schedule pairing rather than hope for it, since that is how the knowledge moves.

Delivered in the field

Case

PSP-independent payment layer for a subscription platform

UK meal-kit subscription platform

A UK meal-kit subscription platform now owns a payment orchestration layer that treats every PSP as a plug-in behind one internal contract. We built that layer while moving millions of live subscriptions to a new provider with zero downtime.