LRU Cache with TTL and Tenant Isolation
Last updated: December 9, 2025
Quick Overview
Implement an LRU cache that supports per-entry TTL expiration and tenant isolation, ensuring one tenant's cache usage cannot evict another tenant's entries.
Wiz
December 9, 202510
9
2,596 solved
Implement an LRU cache that supports per-entry TTL expiration and tenant isolation, ensuring one tenant's cache usage cannot evict another tenant's entries.
Caching is critical for Wiz's scanning performance, but in a multi-tenant system, cache design requires careful isolation. A large tenant's scan results should not evict a small tenant's cached data. This problem tests your ability to extend a classic data structure (LRU cache) with production requirements common in multi-tenant SaaS systems.
What the Interviewer Expects
- Implement a standard LRU cache with O(1) get/put operations
- Add TTL support with lazy expiration
- Implement per-tenant capacity limits within the global cache
- Handle edge cases: expired entries, tenant quota exceeded, empty cache
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- How would you implement proactive TTL cleanup without impacting read latency?
- What if tenants have different cache priorities?
- How would you distribute this cache across multiple servers?
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Practice DSA ProblemsSample Answer
Implementation
```python import time from collections import OrderedDict, defaultdict class TenantLRUCache: def __init__(self, global_capacity, per_tenant_capac...
Design Tradeoffs
Per-tenant eviction (_evict_tenant_lru) is O(n) in worst case because we scan for the tenant's oldest entry. For production, maintain a per-tenant LRU...
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