Edge Computing & Edge Functions Flashcards

What is the primary advantage of running A/B testing logic at the edge rather than at the origin server?

Answer: It reduces latency by making routing decisions closer to the user

Running A/B test routing at the edge avoids an extra round-trip to the origin, reducing latency for every experiment assignment.

Which HTTP header is most commonly inspected by an edge function to serve device-specific content (e.g., mobile vs. desktop)?

Answer: User-Agent

The User-Agent header identifies the client browser and device type, enabling the edge to route or transform responses accordingly.

An edge function needs to share state across multiple requests from different users. What is the recommended approach given that edge workers are stateless?

Answer: Use an edge-accessible key-value store such as Cloudflare KV or Durable Objects

Edge workers are stateless by design, so distributed key-value stores or durable objects provided by the platform are the standard way to persist state at the edge.

What happens to an edge function's in-memory variables between two separate HTTP requests handled by the same edge node?

Answer: They persist only for the lifetime of that request; the next request starts fresh

Edge functions follow a request-scoped execution model, so in-memory state does not survive across separate requests.

Which of the following best describes 'cold start' in the context of edge functions?

Answer: The latency incurred when a function instance is initialized for the first time or after being idle

A cold start is the initialization overhead paid when a new function isolate is spun up, adding latency to the first request handled by that instance.

An edge function returns a subrequest to the origin. How is this typically different from the original client request?

Answer: It is an internal request made by the edge worker to fetch data or assets needed to construct the response

A subrequest is a programmatic fetch initiated by the edge function to retrieve upstream data while the original client connection remains open.

What is 'request collapsing' (also called 'request coalescing') in an edge computing context?

Answer: Combining identical concurrent cache-miss requests into a single upstream fetch

Request collapsing prevents cache stampedes by queuing duplicate concurrent requests and serving them all from one upstream fetch.