How should I practice Timed Cache with Sidecar Cleanup?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Netflix phone screen and onsite interview problems in FastPrep.

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Timed Cache with Sidecar Cleanup

Netflix● MediumFULLTIMEPHONE SCREENONSITE INTERVIEW

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Problem statement

Implement a key-value cache where each entry has its own TTL.

Support the following operations:

SET <key> <value> <ttlSeconds> <now>
GET <key> <now>
CLEANUP <now>

GET is the hot path, so it should not scan the whole cache to remove expired entries. A separate sidecar or background process may perform proactive cleanup.

Return the output lines produced by the operation batch. GET should print the current value or NULL if the key is missing or expired.

Function

runTimedCache(operations: String[]) → String[]

Complete the function runTimedCache in the editor below.

runTimedCache has the following parameter:

String[] operations: cache operations executed in order

Returns String[]: the output lines produced by the batch.

Examples

Example 1

operations = ["SET a 1 5 0", "GET a 3", "GET a 6"]return = ["1", "NULL"]

Key a expires at time 5. It is still valid at time 3 and expired by time 6.

Example 2

operations = ["SET a 1 5 0", "SET b 2 2 0", "CLEANUP 3", "GET a 3", "GET b 3"]return = ["1", "NULL"]

By time 3, key b has expired and may be removed during cleanup. Key a is still alive.

Constraints

GET should stay cheap even when the cache is large.
Each key has a per-item TTL.
A cleanup helper may delete expired entries outside the hot path.