Calendar App Database Design
Design a relational database model for a calendar application that allows users to manage their events, reminders, and invite other users to events.
Ranked Cache System
Design and implement a ranked cache system. Primary goal: store key-value pairs with efficient reads/writes and evict items based on a rank metric (e.g., popularity/frequency/custom). Support Put(key,value,rank), Get(key), Evict(), UpdateRank(key,newRank). Consider both single-instance and distributed modes, with high throughput, low latency, and scalable design.