Airbnb Mobile Engineer Interview Questions

Airbnb app users require efficient battery management to prolong device usage while navigating to their destinations. Optimizing battery usage according to user preferences during their commute is essential.
Use dynamic programming to determine the minimal battery usage when users must traverse a series of n locations with associated batteryCosts that represent the battery consumption to move from one location to the next.
Function signature:
- int minBatteryUsage(int[] batteryCosts):
- Returns the minimum battery usage to navigate through all locations.Example 1:
Input: batteryCosts = [5, 10, 3, 8]
Output: 18
Explanation: In this case, the minimum battery usage is calculated as the sum of the smallest transitions: 5 + 3 + 10 = 18.
Constraints:
- batteryCosts.length <= 10^5
- batteryCosts[i] within [1, 100].

Airbnb handles several user location streams simultaneously to provide accurate search results based on proximity. Merging these streams efficiently is crucial for performance.
Given an array of locationStreams representing UserLocation objects containing longitude, latitude, and timestamp, merge these streams into one sorted array based on timestamp.
UserLocation class:
- class UserLocation:
- float longitude: longitude of the user.
- float latitude: latitude of the user.
- int timestamp: the timestamp when the location was recorded.Example 1:
Input: locations = [[UserLocation(-73.9857, 40.7484, 3), UserLocation(-73.9860, 40.7488, 2)], [UserLocation(-73.9856, 40.7481, 4)]]
Output: [UserLocation(-73.9860, 40.7488, 2), UserLocation(-73.9857, 40.7484, 3), UserLocation(-73.9856, 40.7481, 4)]
Explanation: The merged list is sorted by timestamp.
Constraints:
- locations.length <= 10^4
- locations[i].length <= 10^3
- longitude, latitude within [-180, 180].
- timestamp within [0, 10^9].

Airbnb users often find themselves in areas with poor connectivity. Designing an offline-first synchronization engine ensures that user data is consistently synced and available, regardless of network conditions.
### Class: OfflineSyncEngine
- void saveData(String key, String value):
- Saves data locally when offline and queues it for synchronization.
- void syncData():
- Syncs queued data with the server once connectivity is regained.
- String getData(String key):
- Retrieves the requested data from local storage.### Example 1:
Input:
OfflineSyncEngine syncEngine = new OfflineSyncEngine()
syncEngine.saveData("booking_12345", "Booking details...")
syncEngine.syncData() when restored connectivity after going offline.
Output:
Data should be persistently stored and synced with the server.### Constraints:
- Each user may have up to 10,000 data entries.
- Sync operations should not exceed time limits of 2 seconds ideally, post connectivity restoration.

In Airbnb’s mobile application, users must receive real-time notifications about bookings, cancellations, messages, and promotions. Designing a robust notification system that seamlessly delivers these messages to users at scale is vital.### Class: NotificationManager
- void sendNotification(User user, String message):
- Sends a notification message to the specified user.
- List<Notification> getUserNotifications(User user):
- Returns a list of notifications for the specified user.
- void markAsRead(Notification notification):
- Marks the specified notification as read.
- List<Notification> getUnreadNotifications(User user):
- Retrieves all unread notifications for the specified user.### Example 1:
Input:
User user = new User(1, "Alice")
NotificationManager nm = new NotificationManager()
nm.sendNotification(user, "Your booking is confirmed!")
Output:
nm.getUserNotifications(user) returns List<Notification> containing the confirmation message.### Constraints:
- Users and notifications are uniquely identifiable.
- Each user can have up to 1,000 notifications.