Design concurrent expiring job registry

Design (and discuss how you would implement) an in-memory job registry that supports concurrent access.

Each job has a unique jobId and an expiration time (TTL or absolute timestamp). The system must:

Requirements

• addJob(jobId, payload, expiresAt) : add or update a job with an expiration time.
• getJob(jobId) : fetch job if it exists and is not expired.
• removeJob(jobId) : remove a job.
• A background mechanism (one thread is enough) should delete expired jobs automatically .
• Must be safe under concurrency (multiple threads calling APIs).

Discussion points

• Data structures to make cleanup efficient
• Race conditions between readers/writers and the cleanup thread
• Time complexity and how to avoid O(n) scans