Merlin Entertainments · Engineering

STAY Squad

From zero standards to engineering excellence. The journey, the work, and the vision ahead.

Engineering · August 2024 to Present
Explore

Where we started

A low bar and the opportunity that came with it

When I joined in August 2024, there were no defined engineering standards, no formal processes, and no baseline quality metrics. A maturity assessment quickly revealed how much uplift was possible and the ISO journey stood out as the biggest lever for transformation.

August 2024 · On arrival

The starting position

  • No engineering standards or ways of working in place
  • Unit test coverage unknown and impossible to measure
  • No Azure DevOps repository for frontend code
  • No PR process, branch strategy, or commit conventions
  • Tech design documentation absent or years out of date
  • No observability tooling, completely blind to system health
  • Third party libraries deprecated and untracked
  • ISO journey underway but not being optimised
  • QA handled entirely by the SM/PO with no dedicated resource
  • Maturity assessment score critically low across all pillars
  • No structured approach to frontend code quality, with inconsistent standards and lack of defined classes and IDs across the codebase
Today · Transformed

Where we are now

  • Full engineering Ways of Working defined and adopted
  • Unit test coverage now at 70% with a target of 95%+
  • Azure DevOps repo created and all frontend code tracked
  • PR templates, branch naming and Conventional Commits live
  • Tech Design templates created and ISO now writing documentation
  • Custom Lighthouse dashboard scanning all 15 hotels daily
  • Pa11y accessibility tooling embedded in the IDE workflow
  • ISO working with us to clear third party library debt
  • Acceptance Criteria framework built with structured QA sign-off
  • Observability PoV led with Dynatrace and Datadog under evaluation
  • Reviewing ISO frontend codebase to improve code standardisation, structure, and consistent use of classes and IDs

By the numbers

Progress at a glance

0%
FE unit test coverage
Target 95%+
0
Hotels scanned daily via Lighthouse
0
Environments defined and structured
0
Engineering pillars built from scratch
0
Release pipeline planned for FE
0
Days without standards. That era is over

What has been built

Engineering pillars established by the STAY squad

Every pillar below was built from scratch. Not incremental improvements but foundations that simply did not exist before.

🏗️
Version control and repo
Created the first ever Azure DevOps frontend repository. Branch strategy, Conventional Commits, and a PR template requiring peer review, a Jira link, and test evidence were all established from zero.
Azure DevOpsGit FlowPR Templates
✅
Ways of working
Full engineering Ways of Working documented covering Definition of Ready, Definition of Done, Jira ticket discipline, and code review standards. One ticket per PR. No code ships without a ticket.
DoR / DoDJiraAgile
🧪
Testing and quality
Introduced Jest and React Testing Library. Coverage moved from completely unknown to 70%. Pa11y embedded for accessibility at the IDE level. Peer to peer review on every PR. BrowserStack evaluation underway.
JestRTLSonarQubePa11y
♿
Accessibility at WCAG 2.1 AA
WCAG 2.1 AA adopted as the firm standard. Pa11y embedded in the developer workflow. Semantic HTML, ARIA, focus order, and colour contrast all enforced. Lighthouse accessibility scores tracked daily across all 15 hotel properties.
WCAG 2.1 AAPa11y CILighthouse
📊
Observability dashboard
Built a custom Lighthouse dashboard that scans all 15 Merlin hotel sites daily reporting on performance, accessibility, usability and SEO. Weekly trend reports generated until enterprise tooling such as Dynatrace or Datadog is procured.
Lighthouse APIPerformanceSEO
📋
Tech design documentation
Introduced Tech Design templates where none existed before. ISO now produces structured design docs covering architecture, data models, risks, testing strategy, and rollback plans for every major feature delivered.
ArchitectureTech DebtISO
🔁
QA framework
Built a structured QA Ways of Working with Acceptance Criteria as the single source of truth, a frontend unit test gate, and visual, functional, CMS and accessibility checks. A dedicated QA resource is the next critical hire.
Acceptance CriteriaUATQA WoW
⚡
Performance budgets
Web performance budgets defined (LCP under 2.5s, CLS under 0.1, TTI under 5s on 3G) with mandated frontend optimisations including code splitting, lazy loading, and image optimisation. Focus on reducing CLS and removing render-blocking CSS/JS. JavaScript bundles streamlined by removing duplicate modules and legacy code to improve Core Web Vitals.
Core Web VitalsLCPCLS
🚀
Deployment strategy
Dual pipeline approach to be introduced with a fast frontend release track and a monthly platform update track. Feature flagging to enable safer deployments. Environment strategy to be formalised from local development through QA, UAT, and into production.
CI/CDFeature FlagsEnvironments

The vision ahead

Every scrum team we spin up at Merlin will inherit these standards from day one. No more starting from zero. No more undefined bars.

The STAY squad has proven the model. These engineering pillars become the default template for all future squads, baked into onboarding, tooling, and culture across Merlin Engineering.

Standardised squad templates 95%+ unit test coverage Dedicated QA and SDET hire Dynatrace or Datadog live BrowserStack cross-browser testing ISO maturity uplift continued Full accessibility compliance Dual release pipeline

What is next

Roadmap ahead

The foundations are set. Now we build on them, growing coverage, maturing tooling, and scaling the standard to every new team.

Q2 2026
Observability tooling with Dynatrace or Datadog
PoV complete and procurement in progress. Replacing the custom Lighthouse dashboard with enterprise grade real-time observability across all environments.
PoV led
Q2 2026
Physical devices and BrowserStack for cross-browser and device testing
Budget agreed in principle. Enables full Tier 1 matrix testing across Chrome, Safari, Firefox, Edge, iOS, and Android before every major release.
Pending budget
Q3 2026
Dedicated QA and SDET hire
The QA framework is built and ready. A dedicated engineer is now needed to own it, unlocking regression automation and removing the current SM/PO bottleneck.
Planning
Q2/3 2026
Dual release pipeline with FE fast track live
Separate frontend and platform deployment tracks enabling more frequent frontend releases without being held up by the monthly platform cycle.
Planning
Ongoing
New squad onboarding at scale
Every new scrum team at Merlin Engineering adopts the STAY squad playbook from day one, covering Ways of Working, DoR and DoD, testing standards, observability, and documentation templates.
Evergreen

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