Problem 7

Fix the Broken Cache

HARDDEBUG

Debugging+3

Fix a production bug in a multi-file Python in-memory cache so that all provided tests pass. The repo implements get_user_profile(user_id), which fetches from an upstream client and caches with a TTL. The cache currently has bugs causing incorrect results and flaky behavior. Do not change the public API of get_user_profile and do not modify test files.

Examples

Example 1

Input

Call get_user_profile("u1") twice within TTL

Output

Second call returns cached data without calling the upstream client again

Example 2

Input

p = get_user_profile("u1")
p["name"] = "Hacked"
Call get_user_profile("u1") again within TTL

Output

The returned profile must not include "Hacked"

Note

Caller mutation must not affect the cache.

Constraints

Use Python standard library only
You may edit only non-test source files

Follow-up

How would you adapt this cache to be safe under concurrent access from multiple threads?

Hints

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