Day41
60-day SSE plan
Parking Lot System • URL Shortener • Sliding Window • Tech: Cassandra
Algorithm
DSA
Sliding Window — Minimum Window Substring (LC 76)
Find the smallest substring of s that contains all characters of t.
Example
Input: s="ADOBECODEBANC", t="ABC" → Output: "BANC"
Where it shows up
Token scanning, query parsing, log/event windowing.
Low-level design
LLD
Parking Lot System
Requirements
- Multiple floors, spot types (Car/Bike/Truck).
- Park, unpark, ticketing, fee calculation.
Expectations
- Provide UML class diagram (ParkingLot, Floor, Spot, Vehicle, Ticket, Payment).
- Implement core classes and simulate park/unpark; discuss extendability.
Where it shows up
Real parking garages in malls/airports.
References
High-level design
HLD
URL Shortener
Requirements
- Shorten URLs, redirect keys, optional custom alias, basic stats.
- Scale to millions of reads/day; low latency redirects.
Expectations
- APIs, DB schema, key generation, cache-aside, sharding strategy.
- Trade-offs: SQL vs NoSQL, consistency, TTL, analytics pipeline.
Where it shows up
Bitly/Twitter links, marketing campaigns, QR codes.
Today's deep-dive
Tech
Cassandra
Model a table for user_events with proper partition key; write queries; test CL=QUORUM reads/writes.
Where it shows up
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References