Experience Engineer

Callsign

. Own features end-to-end, from ambiguous requirements to shipped experience.

Posted 10/6/2026contractLondon • United KingdomMid-LevelSeniorWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in JavaScript, TypeScript, and React, with a strong understanding of system design and architecture. Capable of owning features end-to-end while ensuring performance, accessibility, and compliance in regulated industries.

Highest-signal resume keywords

JavaScriptTypeScriptReactSystem DesignRegulated Industry Experience

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills

Frontend DevelopmentBackend ServicesAPI DevelopmentAsynchronous Data FlowsPerformance OptimizationAccessibility Issues DiagnosisUnit TestingComponent TestingEnd-to-End TestingData Visualization

Soft Skills

Product JudgementOwnershipCollaborationProblem SolvingCommunication

Tools & Technologies

CI AutomationTest InfrastructureBuild ConfigurationSDK EngineeringComponent Library Work

Industry Keywords

FintechIdentityPaymentsFraudAuthentication

Tech Stack

Tools & technologies

JavaJavaScriptReactTypeScript

About the role

Key responsibilities & impact

Own features end-to-end, from ambiguous requirements to shipped experience.
Fill design gaps with defensible decisions and deliver coherent flows rather than sets of components.
Contribute actively in refinement by challenging requirements with evidence, proposing simpler alternatives, and bringing product ideas.
Define and measure feature outcomes through usage, feedback, and demo performance.
Understand fraud, identity, authentication, and clients’ operational domains to inform product decisions.
Implement non-trivial components and asynchronous data flows.
Diagnose and fix performance and accessibility issues.
Handle secrets and configuration surfaces safely.
Ship features spanning frontend, backend services, and configuration.
Debug across system boundaries to identify root causes.
Write design documents for significant changes for peer review.
Design test approaches covering unit, component, and end-to-end testing.
Maintain regression suites and fix owned end-to-end failures.
Improve build configuration, CI automation, test infrastructure, and dependencies.

Requirements

What you’ll need

The candidate must already hold the right to work in the UK.
Solid JavaScript/TypeScript and React.
Comfort somewhere beyond the frontend: an API, a service, or infrastructure.
System design and architecture, designing features that span frontend, service and configuration.
Evidence of AI-native working with stated verification.
Ability to design a test approach and defend it.
Product judgement demonstrable from history: UX decisions made and defended without a design spec.
Ownership of a surface or programme through its worst weeks, at any scale.
Java in production; design systems or component library work; SDK or library engineering; or data visualisation.
Experience in regulated industries (fintech, identity, payments).

Benefits

Comp & perks

Pension scheme with Scottish Widows
Private medical cover with Vitality
Life assurance (4x base salary)
Personal Learning & Development Budget
Cycle to Work Scheme
Company Family Leave
25 days annual leave plus Callsign Bank Holiday
Employee Volunteering Program