Calling external APIs from Edge Functions in Supabase - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

What is the output when an Edge Function calls an external API and the API returns a 404 status?

Consider an Edge Function that fetches data from an external API endpoint which does not exist, resulting in a 404 HTTP status. What will the Edge Function's fetch call return?

Supabase

export async function handler(request) {
  const response = await fetch('https://api.example.com/nonexistent');
  return new Response(JSON.stringify({ status: response.status }), { status: 200 });
}

A {"status":200}

B {"status":500}

C Throws a network error

D {"status":404}

💡 Hint

Think about how fetch handles HTTP errors like 404.

The fetch API resolves successfully even if the HTTP status is 404. The response object contains the status code 404, so the Edge Function returns {"status":404}.

❓ Architecture

intermediate

Which architecture best supports calling multiple external APIs in parallel from an Edge Function?

You want to call three different external APIs from a Supabase Edge Function and combine their results. Which approach is best to minimize total response time?

A Use Promise.all to call all APIs in parallel and await their combined results.

B Call each API sequentially using await one after another.

C Call the first API, then call the second and third APIs in parallel after the first finishes.

D Call only the fastest API and ignore the others.

💡 Hint

Think about how to run multiple async calls at the same time.

Using Promise.all runs all fetch calls in parallel, reducing total wait time compared to sequential calls.

❓ security

advanced

What is the safest way to store and use API keys when calling external APIs from Supabase Edge Functions?

You need to call an external API that requires an API key. How should you handle the API key in your Edge Function to keep it secure?

A Hardcode the API key directly in the Edge Function source code.

B Send the API key from the client to the Edge Function in each request.

C Store the API key in Supabase environment variables and access it inside the Edge Function.

D Include the API key in the URL query parameters in the Edge Function.

💡 Hint

Think about where sensitive data should be stored to avoid exposure.

Environment variables keep secrets out of source code and client requests, protecting API keys from exposure.

❓ Configuration

advanced

Which code snippet correctly handles JSON response parsing and errors when calling an external API from an Edge Function?

Choose the code snippet that safely fetches JSON data from an external API and handles possible errors without crashing.

A

const res = await fetch(url);
const data = await res.json();
return new Response(JSON.stringify(data));

B

try {
  const res = await fetch(url);
  if (!res.ok) throw new Error('API error');
  const data = await res.json();
  return new Response(JSON.stringify(data));
} catch (e) {
  return new Response('Error', { status: 500 });
}

C

const res = fetch(url);
const data = await res.json();
return new Response(JSON.stringify(data));

D

const res = await fetch(url);
const data = res.json();
return new Response(JSON.stringify(data));

💡 Hint

Consider error checking and async handling.

Option B checks if the response is OK and uses try-catch to handle errors, preventing crashes.

✅ Best Practice

expert

What is the best practice to avoid cold start delays when calling external APIs from Supabase Edge Functions?

Cold starts can slow down Edge Functions. Which approach helps reduce cold start latency when your function calls external APIs?

A Keep the Edge Function code minimal and use caching for API responses.

B Include large libraries in the Edge Function to handle all API calls.

C Call external APIs only after a long delay inside the function.

D Deploy multiple versions of the Edge Function with different API keys.

💡 Hint

Think about what affects startup time and how caching helps.

Minimal code reduces startup time, and caching API responses avoids repeated slow calls, improving performance.