Fixing Delicate Cache Mismatches in a Brownfield SPA: A Pragmatic Solution

Building in public often means talking about shiny new features, but in mature production applications, the most critical engineering work is usually brownfield problem solving —iterating on top of years and years of code logic and/or production system decisions. On DEV (powered by the open-source Forem codebase), we have a hybrid architecture that blends Rails server rendering, Fastly edge caching, and lightweight client-side navigation (via InstantClick ). This setup delivers sub-100ms page transitions, but partial page swaps combined with aggressive edge caching create delicate deployment c