FlowState ITFlowstate IT

custom software development agency

Custom Software Development, Engineered to Be Inherited

A UK custom software development company that builds bespoke, production-grade systems to a verifiable standard — every material decision recorded, and an asset your next CTO can inherit without archaeology.

What it is

Custom software development, done our way, means a bespoke system built against a named engineering standard rather than assembled and hoped for. Most software engagements fail quietly — not at launch, but eighteen months later, when the original team is gone, nothing is documented, and a security review surfaces problems nobody can trace to a decision. We build to make that outcome impossible: modular, domain-separated, multi-tenant architecture, with the decision trail, threat model, and runbook produced as you go — not reconstructed after the fact.

What’s included

Modular, multi-tenant architecture

Domain-separated services designed to change safely — not a monolith that resists every edit.

OWASP ASVS Level 2 engineering

Role-based access with immutable audit logging, and SAST, DAST, and dependency scanning running in CI.

Infrastructure as Code

Every environment reproducible from code, with defined RPO/RTO and automated backups.

Automated tests with enforced coverage

Structured logging, metrics, error-tracking, and alerting so failures surface before customers notice.

The Governance Pack

Architecture Decision Record, Threat Model, Security Posture Document, Operational Runbook, and Forensic Handover — the evidence an auditor or a new CTO will ask for.

Where it fits

Regulated SaaS

Multi-tenant portals for firms whose customers run security questionnaires — access logs and evidence generated by design.

Ops Automation

Back-office that runs itself: invoicing, reporting, reconciliation, and follow-ups automated end to end, with monitoring built in.

Migration

Take over an undocumented codebase cleanly — we produce the decision trail, threat model, and runbook so your team owns it, not fears it.

Risk reversal

We take the risk. You keep the asset.

Every commitment below is written into the contract — not implied, not verbal. Risk transfers to us during delivery.

90-day warranty

90-Day Defect Warranty

Any defect against the agreed acceptance criteria, found within 90 days of launch, is fixed at no cost.

Critical: 4 business hours · Major: 2 business days · Written into the contract.

100% IP

100% IP Assigned on Payment

You own everything — code, infrastructure, and the full decision trail — assigned to you on payment.

No lock-in. No hostage code. No dependency on us to keep it running.

Per-phase approval

Approve Every Phase Before You Pay

The build is decomposed into phases with written acceptance criteria agreed before each begins. You approve each phase before the next starts.

Invoiced per phase · Stop at any phase boundary.

Stage 0 credited

Stage 0 Credited Against the Build

The Discovery & Technical Audit is a fixed fee, credited in full against your build.

Not the right fit? You keep the architecture proposal, threat model, and roadmap.

Questions, answered

Typical production SaaS engagements run £50,000–£150,000, depending on scope, integrations, and compliance depth. You are invoiced per phase and approve each phase before you pay, so cost tracks the work — and Stage 0 (Discovery & Technical Audit) is a fixed fee credited in full against the build.
Yes — 100% of the IP is assigned to you on payment: code, configuration, and documentation. There is no lock-in and no hostage code; you are never dependent on us to keep your own system running.
We engineer to OWASP ASVS Level 2 and align with the EU AI Act from the first line of code — modular multi-tenant architecture, role-based access with immutable audit logging, SAST/DAST and dependency scanning in CI, Infrastructure as Code, defined RPO/RTO, and automated tests with enforced coverage.
Every launch carries a 90-day post-launch defect warranty. Any defect against the agreed acceptance criteria found within 90 days is fixed at no cost — critical issues within 4 business hours, major issues within 2 business days.
Yes — we are UK-based and UK-supported. Real people, UK hours, no offshore black box.

Related services

You are not buying code. You are buying certainty.

Stage 0 turns your problem into a fixed-price roadmap — credited in full against the build if you proceed.

Book a scoping call