Airbnb Backend Engineer System Design Questions

Airbnb requires an effective notification system for its bookings. You need to create a MessageQueue class that handles messages related to bookings, ensuring that they are processed in the order they were received.
Define a class MessageQueue with the following methods:
- void enqueue(BookingMessage message) - adds a new message to the queue.
- BookingMessage dequeue() - removes and returns the next message from the queue; returns null if the queue is empty.
- bool isEmpty() - checks if the queue is empty.Example 1:
Input: enqueue(new BookingMessage('booking1'))
Output: null
Input: dequeue()
Output: booking1
Input: isEmpty()
Output: falseConstraints:
- The queue can hold up to 10000 messages.

Airbnb relies on quick access to property information across various services. You need to design a Cache class that will manage property data in a manner that it can support common operations while ensuring high performance.
Define a class Cache with the following methods:
- void put(String key, String value) - stores a value in the cache with the given key.
- String get(String key) - retrieves the value associated with a key, returning null if the key does not exist.
- void invalidate(String key) - removes the value for the key, if it exists.Example 1:
Input: put('listing1', 'property A')
Output: null
Input: get('listing1')
Output: property A
Input: invalidate('listing1')
Output: null
Input: get('listing1')
Output: nullConstraints:
- The cache can contain up to 10000 entries.