FinTech software development
Trading platforms, payment systems and real-time data, where correctness and latency both matter.
What FinTech actually demands.
FinTech is the one place where correctness and latency are the same requirement. A balance that's right but three seconds late is wrong. A number that arrives instantly and doesn't reconcile is worse. Every architectural decision here gets made under both constraints at once — and the ones that only satisfy one of them fail in production rather than in review.
The other half is trust. Users hand over exchange API keys, gateway secrets and account balances, then let your software act on their behalf. That raises the floor on everything: how secrets are stored, where they're allowed to be decrypted, who is permitted to do what, and whether you can reconstruct afterwards exactly what happened and why. Security is a requirement, not a phase bolted on at the end with a checklist.
And you are building on other people's systems. Exchanges, payment gateways, banking APIs and market data feeds each bring their own rate limits, error taxonomy, rounding rules and opinions about uptime. Assume they will be slow, wrong or absent at some point — they will be. The engineering that matters is what your platform does on that day.
What we build here.
Crypto trading, payments and real-time data.
Trading platforms and automation engines
Order entry, position views and strategy automation, built so a manual trade and an automated one travel the same path and land in the same history. Strategies live as configurable data, not as code we redeploy to change a parameter. The engine owns the whole order lifecycle — intent, placement, acknowledgement, fill, reconciliation.
- Strategy parameters a trader edits, with no deploy required
- Client order IDs so a retry after a timeout never doubles a fill
- One stop control that halts automation and reports what it found
Real-time data pipelines
REST for state, WebSocket for the stream, and one aggregated channel to the browser rather than a connection per venue. The server merges and throttles the fan-in, so the interface stays responsive when a pair or a feed goes volatile. A socket that stops delivering without ever disconnecting is the failure we instrument for first.
- One socket to the client, many upstream — the server does the merging
- Reconnect, resubscribe and backfill on every drop
- Server-side throttling so the browser doesn't thrash under load
Payments, gateways and integrations
Payment flows, recurring collection, refunds, reconciliation and the third-party integrations underneath them. We design for idempotency and for webhooks that arrive twice, late, or out of order, because that is what webhooks do. State changes are written down before they're acted on, so a crash mid-flight is recoverable rather than forensic.
- Idempotency keys on every money-moving call
- Webhook handling that tolerates duplicates and reordering
- Online and offline payment paths reconciled into one ledger
- Per-provider rate-limit budgets with backoff, not blind retries
Credential custody and secure access
Exchange keys, gateway secrets and LLM tokens stay server-side, encrypted at rest and decrypted only inside the service that needs them. The browser asks the server to act; the server decides whether it may. Authorization is checked server-side on every privileged action — never inferred from a hidden button.
- Keys never serialized to the client
- Proxy layer with origin validation, rate limiting and usage metering
- Trading-scoped, withdrawal-disabled keys recommended at onboarding
- Role-based access enforced on the server, not in the UI
Audit trails and observability
Financial systems fail quietly. A rounding rule that shaves a decimal off every order, a feed that stalls, a scheduled job that skipped a batch — none of those throw an exception. So we instrument for the silent failures specifically, and keep an audit trail that ties every balance change back to the action and the actor behind it.
- Every automated action traceable to the rule that placed it
- Alerts on stalled streams, order rejects and socket health
- Reporting built on the same records as the ledger, not a parallel copy
Work we've shipped in this space.
Real engagements, picked because they were hard.
How we'd engage.
Custom Software & SaaS
Business-critical platforms, engineered MVP-to-scale.
AI Development & Integration
Practical, production-grade AI built into real products — not thin wrappers.
FinTech, answered.
Idempotency keys on every money-moving call, client-supplied order IDs, and webhook handlers that tolerate duplicates and reordering. State changes are written down before they're acted on, so a crash mid-flight is recoverable rather than forensic.
It gets designed for, not discovered. Per-provider rate-limit budgets with backoff, reconnect and backfill on every socket drop, and alerts on stalled streams — a feed that stops delivering without ever disconnecting is the failure we instrument for first.
We build software, not compliance advice. We implement the controls your counsel or compliance lead specifies — access rules, audit trails, data handling, retention — and we say plainly where the software boundary sits. We claim no certifications we don't hold.
Yes. The review covers credential handling, idempotency, reconciliation and stream health alongside the usual architecture and performance work, and we read the code before quoting a rewrite. The answer is often a short list of fixes and a plan, not a rebuild.
Fixed scope with milestone billing while the platform is being built, moving to a dedicated team once it keeps growing. Onboarding is days rather than weeks — we don't run a bench. If the shape you asked for is the wrong one, we say so before you sign it.
Related.
Building in FinTech?
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