Crypto & Bitcoin applications
Wallets, custody flows, on-chain integrations and exchange connectivity with key handling done correctly.
Critical Product Engineering
Systems where a bug costs real money
Some products can't be learned on. Payments, custody, trading, health records and anything handling other people's money need engineers who have shipped it before — and who design for the failure case first.
0security incidents to date
- 0
- security incidents to date
- 99.9%
- uptime targets met
- <50ms
- typical API response
- Senior-only
- engineers on these builds
The challenge
Systems you can't affordto get wrong?
In fintech, crypto and high-traffic products, a slow endpoint or a security gap means lost funds, lost trust and lost customers.
Talk to our expertsSecurity gaps
Weak auth, exposed keys or unaudited code waiting to be found.
Slow under load
Systems that slow down or fail exactly when traffic peaks.
Fragile integrations
Payment, exchange and partner APIs that break in silent, costly ways.
Our solution
See engagement optionsWhat we build for you
High-security, high-performance systems — crypto and fintech workflows, complex APIs, hardened backends and deep performance work.
Fintech workflows
Payments, ledgers, reconciliation, KYC/AML flows and reporting built to survive an audit.
High-security backends
Threat-modelled architecture, encryption at rest and in transit, secrets management and least-privilege access.
Complex API platforms
Versioned public APIs, webhooks, rate limiting, idempotency and documentation partners can build against.
Performance optimisation
Profiling, query tuning, caching layers and architecture changes that turn seconds into milliseconds.
Real-time systems
Streaming data, websockets, order flow and event pipelines that hold up under bursty load.
Scale & reliability engineering
Load testing, autoscaling, failover, observability and incident runbooks before you need them.
Security & code audits
Independent review of an existing system with a prioritized remediation plan and fix support.
How it works
From input to result
What comes in on the left, what goes out on the right — and what we build in the middle, connected to the tools your team already uses.
Map your workflow with us- User transactions
- Partner APIs
- Market data
- Admin actions
Hardened backend
Secure, fast and audited
- Settled payments
- Full audit trail
- Real-time alerts
- Live monitoring
Our process
A simple 5-step process
From first call to production — you see progress every week and know what comes next.
- 1
Threat & load modelling
What can go wrong, what it costs, and what traffic and failure modes the system must absorb.
- 2
Architecture review
Data flows, trust boundaries, key management and the blast radius of every component.
- 3
Build with tests first
Critical paths covered by automated tests and property checks before features stack on top.
- 4
Hardening & verification
Penetration-style review, dependency scanning, load testing and a remediation pass.
- 5
Observability & runbooks
Metrics, alerts, tracing and documented incident response handed to your team at launch.
Who it's for
Real solutions for real business needs
If you recognise yourself here, the first call will be a short one — we already know the questions to ask.
Fintech & crypto founders
Products holding funds or moving money, where security is the product, not a feature.
Tech-led startups
Teams whose differentiation is engineering depth — latency, scale or algorithmic quality.
Existing product owners
Live systems that are slow, fragile or failing under growth and need senior intervention.
Regulated industries
Health, legal and finance operations with compliance and auditability requirements.
Success story
Crypto Wallet & Trading App
Fintech / crypto · USA
A secure Bitcoin/crypto wallet with real-time trading, biometric auth and hardware-grade key handling.
- 4.8★
- app store rating
- 80k+
- downloads
- 0
- security incidents
Engagement options
Pick the entry point that fits your stage
Start small and prove it, or go straight to the build. Fixed scope, clear deliverables.
Architecture & Security Review
One-time · 1–2 weeks
An independent read of your system with risks ranked by likelihood and blast radius.
- Threat model & findings
- Prioritized remediation plan
- Effort & cost estimates
Critical Build
Project · 12+ weeks
Senior-only engineering of the high-stakes core, with testing and hardening built into the price.
- Senior-only team
- Test & load coverage
- Observability & runbooks
Performance Rescue
Fixed price · 2–4 weeks
A focused intervention on a slow or unstable production system, with measured results.
- Profiling & bottleneck map
- Implemented fixes
- Before/after benchmarks
Technologies
Built on proven, well-supported tools
JavaSpring BootNode.jsLaravelPHPPostgreSQL
FAQ
Common questions
Quick answers about Critical Product Engineering. Don't see yours? Ask us directly.
Ask a questionCan you sign an NDA and work under our security policy?
Yes. NDAs, background-checked engineers, VPN or VDI access, dedicated devices and working inside your cloud accounts are all normal for these engagements.
Do you replace a formal third-party security audit?
No, and we'd distrust anyone who said otherwise. We build to pass one and remediate findings, but the independent audit should stay independent. We'll recommend firms we've worked alongside.
Our system is already live and struggling. Can you help without a rewrite?
Usually. Most performance problems are a handful of queries, a missing cache layer or a bad hot path — not the architecture. The Performance Rescue package finds out in two weeks, and a rewrite recommendation comes with evidence.
How do you handle key material and secrets?
HSMs or managed KMS for key material, no secrets in code or CI logs, least-privilege IAM, and rotation policies documented at handover. For custody work, multi-sig and threshold schemes are designed in from the start.
Let's build
Get 3 AI & product ideas for your business — free.
Book a discovery call or get an MVP blueprint. No pressure, no jargon — just a clear plan for your idea, workflow or product.
Prefer email? hello@nexalinx.com