Java Frontend Engineer

#W2 RoleJob Title: Senior Frontend Engineer Real-Time Web ApplicationsLocation: Malvern,PAJob DescriptionWe are looking for a Senior Frontend Engineer with strong experience building production-quality JavaScript applications used in real-world environments. This role will focus on enhancing and scaling a Flask-backed, vanilla JavaScript dashboard that supports engineers during live production incidents.The ideal candidate should have hands-on experience working on real-time web applications, especially in high-pressure operational environments. This position involves taking ownership of an existing dashboard, migrating it from polling-based updates to real-time push architecture, versioning APIs for broader external usage, and evolving the platform into a self-service solution for multiple teams.This is a strong fit for someone who is highly effective with core JavaScript and browser fundamentals, without depending heavily on frontend frameworks. The current codebase is built in vanilla JavaScript, and that approach is expected to continue unless a very strong technical justification is presented.Key ResponsibilitiesOwn, maintain, and enhance a production dashboard built with vanilla JavaScript and FlaskMigrate the application from polling-based updates to real-time push mechanisms such as WebSockets or Server-Sent Events (SSE)Design and support versioned frontend API integrations for external platform consumptionBuild scalable self-service capabilities for multiple internal teamsWork across the full stack by reading, modifying, and extending Flask route handlers and Jinja2 templatesImprove UI responsiveness and usability for engineers operating during active production incidentsProfile and optimize frontend performance by identifying true bottlenecks and implementing targeted fixesCollaborate with backend and platform teams to improve API design, response handling, and system reliabilityRequired Skills8+ years of experience building production-grade frontend applicationsStrong proficiency in JavaScript, with deep understanding of DOM manipulation, event loop, fetch lifecycle, and browser renderingProven experience building and supporting real-time web applications using WebSockets or SSE in productionStrong knowledge of connection lifecycle management, reconnection handling, heartbeat mechanisms, and client-side state recoveryExperience consuming or designing versioned APIs, including understanding breaking vs. non-breaking changesAbility to write API specifications before implementation and support version migrations from the consumer sideExperience working on incident response, operations, or observability tools such as Datadog, Grafana, PagerDuty, Splunk, or similar platformsHands-on experience with Flask and Jinja2 templates; able to work effectively in lightweight Python web environmentsStrong frontend performance tuning and profiling skills, including browser rendering analysis, network waterfall investigation, and API response optimizationPreferred QualificationsExperience building dashboards or operational tools used during production incidentsFamiliarity with self-service platform development for multi-team usageAbility to work independently in an existing codebase and drive modernization efforts with minimal supervision.