A
Applied software engineering
Backend services, data models and user-facing applications written to be read, tested and changed by other engineers years after release.
DOOR 47 LTD · Software engineering
Systems built to be understood, operated and changed
We design, build and maintain software and cloud systems for organisations whose work depends on them. Every engagement produces working software, documented decisions and a team that can continue without us.
- Discipline
- Software & systems engineering
- Delivery
- Increments, not milestones
- Contact
- [email protected]
01Company overview
An IT company organised around engineering, not around selling projects
DOOR 47 LTD works on the parts of technology that are difficult to outsource: the architecture of a system, the reliability of its data, the cost of running it and the ability of a team to keep changing it. Our work covers custom software development, web applications, cloud delivery, integration and technical support.
We prefer engagements where the problem is concrete — a process that does not scale, a system that cannot be modified, data spread across tools that do not speak to each other. In those situations the value of good engineering is measurable rather than rhetorical.
What we produce is deliberately unglamorous: readable code, explicit interfaces, reproducible environments, tests that describe real behaviour and documentation written for the person who arrives next. Those are the artefacts that decide what a system costs over its lifetime.
02Core areas of expertise
B
System architecture
Boundaries, contracts and failure behaviour decided before code is written, so that scaling and change stay predictable.
C
Cloud and delivery
Reproducible environments, automated deployment and observable runtime behaviour across managed cloud infrastructure.
D
Integration and modernisation
Connecting existing systems and carefully replacing the parts of them that have become too expensive to keep.
03Services
Nine service areas, one engineering practice
Each area is described in full on the Services page, including scope, approach and the situations it suits.
- 01
Custom software development
Product and internal systems built around a specific operational reality.
- 02
Web application development
Browser-based applications with clear state, accessible interfaces and measurable performance.
- 03
Cloud solutions
Environment design, automation, cost visibility and operational readiness.
- 04
System architecture
Decomposition, data flow, contracts and documented technical decisions.
- 05
API and systems integration
Reliable exchange of data between internal and third-party systems.
- 06
Legacy software modernisation
Incremental replacement of aging components without stopping the business.
- 07
Technical consulting
Independent review of architecture, delivery practice and technical risk.
- 08
Quality assurance
Automated and exploratory testing tied to the behaviour that matters.
- 09
Maintenance and support
Monitoring, corrective work and planned change after launch.
04Technology capabilities
Tools chosen for the problem, not for the résumé
We work with a deliberately conventional stack. Familiar technology with a long support horizon is easier to hire for, easier to operate and easier to hand over than anything selected for novelty.
- Languages
- TypeScript, JavaScript, Python, Go, Java, SQL
- Frontend
- React, component systems, design tokens, accessibility tooling
- Backend
- REST and GraphQL services, event-driven workers, background processing
- Data
- PostgreSQL, MySQL, Redis, object storage, analytical pipelines
- Cloud
- Containerised workloads, infrastructure as code, CI/CD pipelines
- Operations
- Structured logging, metrics, tracing, alerting and runbooks
05Working process
Six stages, each with an output someone else can use
- 01
Discovery
We map the current systems, constraints, data and the decisions already made. Nothing is designed before it is understood.
- 02
Definition
Scope, architecture and delivery sequence are written down, together with the risks we expect and how we intend to handle them.
- 03
Construction
Work moves in short increments. Each increment is reviewed, tested and deployable rather than a demo.
- 04
Verification
Behaviour is tested against the agreed requirements, including failure paths, data integrity and performance under load.
- 05
Transition
Documentation, environments, credentials and operational knowledge are handed over so your team is never dependent on ours.
- 06
Operation
Where required, we stay involved for monitoring, corrective work and planned evolution of the system.
06 · Position
A system is finished when another team can operate it, extend it and explain it without calling us.
07Business challenges we solve
Systems that no one can safely change
Undocumented behaviour and missing tests turn small requests into long projects. We rebuild the understanding first, then the code.
Data that disagrees with itself
When several systems each hold a partial truth, reporting stops being trustworthy. Integration work starts by deciding where each fact lives.
Manual steps holding a process together
Spreadsheets and copy-paste between tools are a sign of a missing system boundary, not a training problem.
Infrastructure cost without visibility
Environments that grew by accident are expensive and fragile. Reproducible infrastructure makes both cost and behaviour explicit.
Releases that everyone dreads
Long, manual release procedures are a delivery design problem. Automated pipelines and reversible deployments remove the ceremony.
Software that cannot be handed over
Knowledge held by one person is a business risk. We write things down as part of the work, not after it.
08Industries and use cases
Contexts where this kind of work applies
The technical problems below recur across sectors. What changes is the vocabulary, the regulatory pressure and the tolerance for downtime.
- Logistics and operations
- Scheduling, tracking, document flow and integration with carrier and warehouse systems.
- Professional services
- Client-facing portals, internal case handling and reporting across fragmented tools.
- Retail and commerce
- Catalogue, order and fulfilment systems connected to accounting and stock.
- Manufacturing and field work
- Data capture from equipment and technicians, and consolidation into usable records.
- Digital products
- Multi-tenant applications, billing-adjacent logic and platform APIs.
- Internal IT functions
- Automation of processes that currently depend on manual coordination.
09Engineering principles
Rules we apply before anyone asks us to
Clarity before cleverness
Code is read far more often than it is written. Obvious solutions survive team changes.
Small, reversible steps
Every change should be deployable and undoable. Large irreversible moves are avoided by design.
Explicit boundaries
Modules and services own their data and expose contracts. Shared mutable state is treated as a defect.
Automate what repeats
Tests, builds, deployments and checks belong in pipelines, not in someone's memory.
Design for failure
Timeouts, retries, idempotency and degraded modes are part of the specification, not an afterthought.
Documentation as deliverable
Decisions, interfaces and operational procedures are written alongside the system.
10Security and quality
Security and quality treated as engineering work
Access control, input validation, secret handling and data minimisation are designed with the feature they belong to. Dependencies are tracked and updated, and secrets stay outside source control.
Quality is enforced by automation: type checking, unit and integration tests, pipeline gates and code review. Where a system processes personal data, we help define what is stored, for how long and who can reach it.
We describe what our practices are and do not claim certifications or audits we do not hold.
11Why work with DOOR 47 LTD
Engineering-led
Technical decisions are made by the people who will maintain the result, and explained in language you can act on.
Transparent scope
What is included, what is deferred and what is uncertain is written down before work starts.
No lock-in
Code, infrastructure definitions, credentials and documentation belong to you from the first commit.
Continuity
We work in a way that lets your team take over at any point without a rescue project.
12Contact information
Written enquiries by email
Email is the only channel we operate. A short written description of the system, the problem and the constraints is enough for us to reply with a technical assessment rather than a questionnaire. Full guidance is on the Contacts page.
- Company
- DOOR 47 LTD
- [email protected]
- Domain
- door47.com