Airbnb Backend Engineer Interview 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.

Airbnb must effectively manage bookings to reduce the chance of double bookings on properties. We need to identify gaps or overlaps in bookings to optimize resource allocation.
Given a list of bookings with start and end dates, implement a function to find all overlapping bookings. If bookings overlap, record the conflicts.
- List<List<Booking>> findOverlappingBookings(List<Booking> bookings) - returns a list of lists, where each sub-list contains bookings that overlap.Example 1:
Input: bookings = [(1, 5), (3, 7), (6, 10), (8, 12)]
Output: [[1, 5], [3, 7], [6, 10], [8, 12]]
Explanation: Bookings (1,5) and (3,7) overlap; (6,10) and (8,12) overlap too.Example 2:
Input: bookings = [(1, 2), (2, 3), (4, 5)]
Output: []
Explanation: There are no overlapping bookings.Constraints:
- 1 <= number of bookings <= 10^4
- Start and end dates are unique integers.

Airbnb needs a reliable way to suggest listings based on users' current location and preferred neighborhoods. This can enhance user experience by showing them properties that are not only available but also suitable to their tastes.
Given a graph where nodes represent properties and edges represent distances between them, implement a function to find properties that are within a certain distance from a given location. The graph can have varying distances between nodes to reflect real geographical positioning.
- List<Property> findAvailableProperties(String location, int maxDistance) - returns a list of properties available within the specified distance from the given location.Example 1:
Input: location = 'Central Park', maxDistance = 2
Output: ['Listing A', 'Listing B', 'Listing C']
Explanation: Properties A, B, and C are within 2 kilometers of Central Park.Example 2:
Input: location = 'Brooklyn Bridge', maxDistance = 1
Output: ['Listing D']
Explanation: Only Listing D is available within 1 kilometer of Brooklyn Bridge.Constraints:
- 1 <= number of properties <= 10^5
- 1 <= maxDistance <= 100
- Property names are unique strings.