Edge Computing & Edge Functions Flashcards

What is WebAssembly (Wasm) used for in edge computing environments?

Answer: Running code compiled from languages like Rust or C at near-native speed inside edge sandboxes

Wasm allows high-performance, sandboxed execution of code written in systems languages, expanding the set of workloads suitable for edge functions.

Which of the following is a key limitation of edge functions compared to traditional server-side applications?

Answer: They typically have restricted CPU time limits and cannot run long-lived background processes

Edge functions have strict CPU time budgets (often milliseconds) and are not designed for long-running or stateful background workloads.

What is 'origin shield' and how does it interact with edge functions?

Answer: A designated mid-tier PoP that consolidates cache misses from all edge nodes before hitting origin, reducing origin load

Origin shield acts as a second caching layer between edge PoPs and the origin, so cache misses from hundreds of edges are funneled through one shield node.

How do edge functions typically handle authentication tokens such as cookies without violating the CDN's caching model?

Answer: By stripping cookies before caching and re-attaching or validating them using the edge function

A common pattern is to strip auth cookies at the edge, serve a cached response, and then use the edge function to re-inject user-specific data or validate the token before delivery.

Which standard API do Cloudflare Workers and other edge platforms expose for making outbound HTTP calls from an edge function?

Answer: The Web Fetch API (fetch())

Edge function runtimes implement the Web Fetch API (same as browsers) for making outbound HTTP requests, keeping the API surface standard and portable.

What is cache poisoning via edge function and how is it prevented?

Answer: Injecting malicious content into CDN cache by manipulating request headers that are inadvertently included in the cache key

If an edge function uses attacker-controlled headers as cache keys, an attacker can serve malicious cached responses; prevention requires strict cache key normalization.

An edge function needs to perform image resizing. Which approach is most appropriate given edge resource constraints?

Answer: Use the CDN platform's built-in image transformation service or a Wasm-compiled image library within size limits

Edge functions have memory and bundle size limits, so either the platform's native image API or a lightweight Wasm library is the practical choice.