Ship Without Stopping: A Practitioner's Framework for Feature Flag-Controlled Frontend Modernization
Author(s): Parth Patel, Althaf Khan Pattan
Publication #: 2606043
Date of Publication: 08.11.2023
Country: United States
Pages: 1-9
Published In: Volume 9 Issue 6 November-2023
DOI: https://doi.org/10.62970/IJIRCT.v9.i6.2606043
Abstract
Replacing a frontend JavaScript framework in a live production system is one of the most demanding modernization tasks a development team faces. Unlike backend migrations, frontend replacements carry problems that server-side thinking misses: two rendering runtimes may share a browser session, client-side state is hard to reconcile across framework boundaries, and a failed deployment reaches users instantly with no retry window. Existing migration research covers backend and database contexts but not the frontend specifically. This paper presents FlagFirst, a five-phase framework that uses feature flags as the primary control mechanism for progressive, reversible frontend framework replacement. We define four flag granularity levels, component, route, bundle, and runtime, and show how each affects rollback speed, JavaScript payload overhead, and blast radius. A 14-month production case study of an AngularJS-to-React migration validates the framework, showing zero unplanned outages, a 340 ms gain in Largest Contentful Paint, and a single automated rollback that completed in under three seconds.
Keywords: feature flags, feature toggles, frontend migration, zero downtime deployment, progressive delivery, JavaScript framework migration, canary release, continuous delivery, software modernization, AngularJS to React, blue-green deployment, rollback strategy, dual runtime coexistence, strangler fig pattern
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