Mid · Concurrency

Async, Await & Cancellation

Design an asynchronous HTTP operation that propagates cancellation, handles failures, and avoids blocking the request thread.

Examples

Baseline approach

Begin by explaining the core mechanism, stating assumptions, and walking through one concrete example.

Time: Depends on design · Space: Depends on design

public async Task<string> FetchAsync(
    HttpClient client, Uri uri, CancellationToken ct)
{
    return await client.GetStringAsync(uri, ct);
}

Strong answer

Propagate cancellation through every async operation. Reuse managed HttpClient instances. Define timeout and retry policy at the service boundary.

Time: Discuss operation costs · Space: Discuss retained state

public async Task<string> FetchAsync(
    HttpClient client, Uri uri, CancellationToken ct)
{
    return await client.GetStringAsync(uri, ct);
}

Task.Result can block; async does not automatically create a new thread.
State assumptions and justify trade-offs rather than memorizing a single answer.