Idempotency for safe retries in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the key concept that ensures safe retries without side effects.

HLD

To make an operation safe for retries, it must be [1].

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Aasynchronous

Bidempotent

Cstateful

Dblocking

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing idempotent with asynchronous or stateful operations.

An idempotent operation can be repeated multiple times without changing the result beyond the initial application. This ensures safe retries.

2fill in blank

medium

Complete the code to show how to use a unique identifier to achieve idempotency.

HLD

Store the result of a request using a unique [1] to avoid duplicate processing.

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Atimestamp

Buser password

Csession token

Didempotency key

Attempts:

3 left

💡 Hint

Common Mistakes

Using timestamp or session token which do not guarantee uniqueness per request.

An idempotency key uniquely identifies a request so that retries with the same key do not cause duplicate effects.

3fill in blank

hard

Fix the error in the statement about idempotency in distributed systems.

HLD

In distributed systems, to ensure idempotency, the system must [1] requests with the same idempotency key.

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Aignore duplicate

Bprocess all

Clog and discard

Dretry indefinitely

Attempts:

3 left

💡 Hint

Common Mistakes

Processing all duplicates causes repeated side effects.

The system must ignore duplicate requests with the same idempotency key to avoid repeated side effects.

4fill in blank

hard

Fill both blanks to complete the idempotency implementation snippet.

HLD

if request.[1] in cache:
    return cache[request.[2]]

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Aidempotency_key

Brequest_id

Cuser_id

Dsession_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using different keys for check and fetch causes errors.

The idempotency_key is used to check and retrieve cached results to avoid duplicate processing.

5fill in blank

hard

Fill all three blanks to complete the idempotent request handling logic.

HLD

def handle_request(request):
    key = request.[1]
    if key in [2]:
        return [3][key]
    result = process(request)
    [2][key] = result
    return result

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Aidempotency_key

Bcache

Ccache_store

Dsession

Attempts:

3 left

💡 Hint

Common Mistakes

Using different cache names or wrong key names causes errors.

The idempotency_key identifies the request. The cache stores results to return on retries, ensuring idempotency.