Edge Computing & Edge Functions Flashcards

Which isolation technology do most CDN providers (e.g., Cloudflare Workers, Fastly Compute) use instead of containers for edge functions?

Answer: V8 Isolates

V8 Isolates provide lightweight, low-overhead sandboxing within a single process, enabling fast cold starts compared to containers or full VMs.

A CDN edge function must validate a JWT on every request. Where should the signing secret be stored securely?

Answer: In a platform-provided secrets or environment variable store

Secrets must be injected at deploy time via the platform's secure environment variable or secrets management service, never hardcoded in source.

What is the purpose of the waitUntil() API available in many edge function runtimes?

Answer: To allow background async work such as logging to continue after the response is sent to the client

waitUntil() extends the function's lifetime beyond the response so async tasks like analytics or cache warming can complete without blocking the user.

An edge function intercepts a request and must forward a custom header to the origin for tracing. Which step is required?

Answer: Clone and mutate the Request object, then pass it to fetch()

Request objects in edge runtimes are immutable, so you must clone them and append the desired headers before passing to fetch().

Which metric best measures the real-world performance improvement gained from moving business logic to the edge?

Answer: Time To First Byte (TTFB) decrease experienced by end users

TTFB directly reflects how quickly users receive the first byte of a response, making it the clearest indicator that edge processing reduced latency.

What is 'edge-side rendering' (ESR)?

Answer: Generating dynamic HTML responses at the CDN edge node rather than at the origin

ESR moves HTML generation to the edge, reducing the round-trip to origin and delivering personalized or dynamic pages with lower latency.

A company wants to enforce geo-blocking at the edge to comply with licensing restrictions. Which data source does the edge function typically query?

Answer: A MaxMind or equivalent IP-to-country database available on the edge platform

CDN platforms provide IP geolocation databases (often powered by MaxMind) as built-in metadata on each request, enabling fast country-level decisions.