Airbnb Software Engineer System Design Questions

Building a modern socially-influenced experience for Airbnb is vital to trawl through user-generated content from experiences (such as reviews and photos). This involves creating a class-based structure for managing a user's feed aligned with their interests.
Problem statement: implement a class to handle a simple Twitter-like feed that allows users to create a post, display the feed, and follow other users.
- class TwitterFeed:
- def __init__(self): - Initializes the object.
- def post(self, user_id: int, post: str): - Creates a new post for the specified user.
- def follow(self, follower_id:int, followee_id:int): - Allows one user to follow another.
- def get_feed(self, user_id: int) -> List[str]: - Retrieve the latest n posts from followed users.Example 1:
Input:
twitter = TwitterFeed()
twitter.post(1, "Looking for cozy places in Paris!")
twitter.post(2, "Trying out local cuisine.")
twitter.follow(1, 2)
print(twitter.get_feed(1)) // returns ["Trying out local cuisine."]Example 2:
Input:
twitter.follow(1, 3)
print(twitter.get_feed(1)) // returns [] since user 3 has no posts.Constraints:
- 1 <= user_id <= 10^4
- posts per user = 100
- followed users = 50

Airbnb needs to optimize its API by implementing a caching mechanism for property listings to reduce database load and improve response time.
Problem statement: Implement an LRU (Least Recently Used) cache with a specified capacity. The cache should support get(key) and put(key, value) operations.
- class LRUCache:
- def __init__(self, capacity: int): - Initializes the LRUCache with the maximum capacity.
- def get(self, key: int) -> int: - Returns the value of the key if the key exists in the cache, otherwise return -1.
- def put(self, key: int, value: int): - Update the value of the key if it exists, otherwise add the key-value pair to the cache. When the cache reaches its capacity, it should invalidate the least recently used item before inserting a new item.Example 1:
Input:
cache = LRUCache(2)
cache.put(1, 1)
cache.put(2, 2)
cache.get(1) // returns 1
cache.put(3, 3) // evicts key 2
cache.get(2) // returns -1 (not found)Example 2:
Input:
cache.put(4, 4) // evicts key 1
cache.get(1) // returns -1 (not found)
cache.get(3) // returns 3
cache.get(4) // returns 4Constraints:
- 1 <= capacity <= 3000
- 0 <= key <= 10^4
- 0 <= value <= 10^4