What is the purpose of the `async` and `await` keyword in JavaScript??

0-2 years experience

1. 1We need to fetch a user's profile from `/api/user` and then display it. Walk me through how you'd write that using async/await.
2. 2If you call an async function but omit the await keyword, what does the caller receive and why?
3. 3Consider this snippet: `async function foo() { return 42; } console.log(foo());` What will be logged and why?

2-5 years experience

1. 1You added async/await to a data‑processing pipeline, but the overall latency increased. What could be causing the slowdown?
2. 2During debugging you see an unhandled promise rejection coming from a function that uses await. How would you locate and fix the issue?
3. 3Why might mixing `.then()` chains with `await` in the same function lead to subtle bugs?

5-8 years experience

1. 1Design a reusable wrapper for API calls that adds a timeout and automatic retries, using async/await. What trade‑offs would you consider?
2. 2In a high‑traffic Node.js service, how would you limit the number of concurrent async operations to avoid exhausting resources?
3. 3Explain how async/await interacts with the Node.js event loop and what impact that has on throughput under load.

8+ years experience

1. 1Our legacy codebase relies heavily on callbacks. How would you plan a migration to async/await while keeping the system stable?
2. 2When building a cross‑team library for asynchronous workflows, how do you expose an API that works well with async/await but also supports older environments that lack native support?
3. 3What architectural considerations arise when you need to coordinate many async/await‑based microservices that have different latency and failure characteristics?