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References: Bandwidth Optimization, Offline Queues, and Service Workers

  1. Service Worker - Wikipedia - The browser feature that powers xAPI offline queues; covers lifecycle events (install, activate, fetch), scope, and the security constraints that govern background sync.

  2. IndexedDB - Wikipedia - The persistent client-side database every serious offline xAPI queue eventually uses; explains object stores, transactions, and the key/index model the chapter's queue implementation relies on.

  3. HTTP/2 - Wikipedia - The protocol that makes statement multiplexing cheap and changes the bandwidth math for high-frequency events. Required reading before deciding how aggressively to batch.

  4. High Performance Browser Networking - Ilya Grigorik - O'Reilly Media - The single most relevant book for this chapter; chapters on TCP, TLS, HTTP/2, and mobile networks ground every bandwidth-optimization decision a textbook author makes.

  5. Web Performance in Action - Jeremy Wagner - Manning Publications - Practical playbook for measuring and reducing payload size, optimizing critical paths, and the field-validated patterns that apply directly to xAPI traffic.

  6. MDN Service Worker API - Mozilla Developer Network - Authoritative reference for service worker registration, lifecycle, and the fetch event; the spec is hard, this docs site is approachable.

  7. MDN IndexedDB Documentation - Mozilla Developer Network - Step-by-step guide to opening databases, structuring transactions, and the upgrade-version migration pattern xAPI offline queues need when the schema evolves.

  8. Workbox - Google Chrome Developers - High-level service-worker library that handles the boilerplate around runtime caching and background sync; valuable for textbook authors who don't want to write a queue from scratch.

  9. web.dev — Offline Cookbook - Google web.dev - Curated collection of offline patterns (cache-first, network-first, stale-while-revalidate) with code samples. Maps directly onto xAPI flush strategies.

  10. Background Sync API - Mozilla Developer Network - The browser API that lets a service worker flush a queued xAPI batch the next time the device is online, without needing the original tab to be open.