eBay SWE Assessment (Industry Coding Assessment)

I took the eBay SWE Industry Coding Assessment on CodeSignal. The problem was to implement a data storage system supporting basic operations, filtering, and point-in-time recovery (backups).

Level 1: Basic Storage (CRUD)

• SET_OR_INC(key, field, value): Update string fields or increment integer fields.
• GET(key, field): Retrieve a field’s value.
• DELETE(key, field): Remove a field or entire key if no fields remain.

Level 2: Scanning & Filtering

• FETCH(field, value): Return records matching a field-value pair, formatted as "field1(val1), field2(val2)", sorted alphabetically by key.

Level 3: Advanced Filtering or TTL

• Either add TTL support to SET, where expired entries behave as deleted, or support multi-field/range filters like value > 100.

Level 4: Point-in-Time Snapshots

• BACKUP(): Save current state and return a backup ID.
• RESTORE(backupId): Revert to a previous state efficiently—deep copy may cause performance issues; better strategies involve versioned maps or Copy-on-Write.

The problem statement resembled what's described in sources like Gemini. I struggled with passing all test cases in Level 4 related to backup/restore performance and correctness. My total score was 510 out of 600.