How One Developer Built a Token-Caching Auth Pipeline Using ASP.NET Core and Playwright

A developer building a React Native app for a football management platform needed a reliable way to handle authentication against an external service that lacked a developer-friendly API. The solution uses an ASP.NET Core backend as a middleware layer, shielding the mobile client from all authentication complexity. When a login request arrives, the backend checks MongoDB for a stored access token; if valid, it is reused immediately, avoiding redundant browser automation. If no token exists or the existing one has expired, Playwright automates the browser-based login flow, retrieves a fresh token, and stores it alongside its expiry timestamp. This architecture reduces latency for returning users, limits load on the external service, and centralises token lifecycle management entirely within the backend.