Designing Airbnb is a classic System Design interview task that brings together geosearch, availability management, dynamic pricing and trust system. It is a two-sided marketplace with unique technical challenges.
Source
Acing the System Design Interview
A detailed analysis of Airbnb design is in the book by Zhiyong Tan.
Key Features of Airbnb
1Functional Requirements
Guest Flow
- •Search by location, dates, number of guests
- •Filtering (price, type of housing, amenities)
- •View listing with photos and reviews
- •Booking and payment
- •Messenger with host
Host Flow
- •Creating and editing a listing
- •Manage your availability calendar
- •Setting up pricing rules
- •Confirmation/rejection of bookings
- •Receiving payments
2Non-functional requirements
Low Latency Search
Geosearch < 200ms. Users expect instant results when changing a map.
High Availability
99.99% uptime. Bookings mean money, downtime is unacceptable.
Consistency
You can't sell the same night twice. Strong consistency for bookings.
System scale
3Geo Search: Search by location
Related topic
Proximity Service
Alex Xu discusses geosearch in detail in the chapter on Proximity Service.
Approaches to geoindexing
| Approach | Description | Use Case |
|---|---|---|
| Geohash | String representation of coordinates, prefix matching | Redis, simple queries |
| Quadtree ✓ | Recursive division of space into 4 parts | In-memory search, Uber |
| S2 Geometry | Google's library, hierarchical cells | Google Maps, Foursquare |
| PostGIS | PostgreSQL extension with R-tree indexes | Small scale |
Airbnb Search Architecture
- 1Elasticsearch as the main search engine with geo_point type
- 2geo_bounding_box query for the visible area of the map
- 3Availability filter - join with availability calendar
- 4Ranking — ML model for personalizing results
Elasticsearch Query Example
{
"query": {
"bool": {
"filter": [
{
"geo_bounding_box": {
"location": {
"top_left": { "lat": 40.73, "lon": -74.1 },
"bottom_right": { "lat": 40.01, "lon": -73.12 }
}
}
},
{ "term": { "property_type": "entire_home" } },
{ "range": { "price": { "gte": 50, "lte": 200 } } },
{ "range": { "guests": { "gte": 2 } } }
]
}
}
}4Availability Calendar
Related case
Hotel Booking
A similar problem of availability management is discussed in the Hotel Booking case.
⚠️ Main difficulty
The calendar must be eventually consistent for reading (search), but strongly consistent for writes (booking). You can't sell the same night twice!
Data Schema
-- Calendar by day
CREATE TABLE availability (
listing_id UUID,
date DATE,
status ENUM('available',
'blocked', 'booked'),
price DECIMAL,
min_nights INT,
PRIMARY KEY (listing_id, date)
);
-- Search index
CREATE INDEX idx_available
ON availability(date, status)
WHERE status = 'available';Optimizations
- •Date ranges: Store intervals instead of individual days
- •Bitmap: 365 bits per year, fast operations
- •Caching: Redis for hot listings
- •Sharding: By listing_id for isolation
Synchronization with search
Elasticsearch should not store the full calendar because it changes too often. Instead, a two-step approach is used:
- 1ES returns candidates by geo + filters
- 2Availability Service filters by calendar (batch lookup)
- 3Ranking Service sorts the final results
5Booking Flow: Reservations
Instant Book vs Request to Book
Instant Book
The guest books immediately, the host does not confirm.
- + Best UX for guests
- + Higher conversion
- - Risk for hosts
Request to Book
The host must confirm the booking.
- + Control for hosts
- - Delay for guests
- - Lower conversion
Booking Process (Instant Book)
- 1Check availability: Atomic check + date locking (Redis SETNX or SELECT FOR UPDATE)
- 2Calculate price: Base price + cleaning fee + service fee + taxes
- 3Payment authorization: Stripe PaymentIntent (hold, not charge)
- 4Create reservation: Transaction: booking + update availability
- 5Notifications: Email/push to guest and host
- 6Payment capture: Charge after check-in (or 24h before)
Distributed Transactions
A reservation touches several services. The Saga pattern is used:
Saga: CreateBooking
├── Step 1: Reserve dates (Availability Service)
│ └── Compensate: Release dates
├── Step 2: Authorize payment (Payment Service)
│ └── Compensate: Cancel authorization
├── Step 3: Create booking (Booking Service)
│ └── Compensate: Delete booking
└── Step 4: Send notifications (Async, no compensate)6Dynamic Pricing Engine
Price components
Host sets:
- Base nightly rate
- Weekend pricing
- Weekly/monthly discounts
- Cleaning fee
- Extra guest fee
Airbnb adds:
- Service fee (guest): ~14%
- Service fee (host): ~3%
- Occupancy taxes
- Currency conversion
Smart Pricing (ML)
Airbnb offers hosts automatic pricing based on:
- Seasonality
- Events in the city
- Day of the week
- Occupancy rate
- Lead time
- Competitors
- Rating
- Amenities
- Photo quality
7Trust & Safety System
Two-way trust
For guests:
- Verified photos
- Reviews from other guests
- Superhost badge
- Airbnb Cover (insurance)
- 24/7 support
For hosts:
- ID verification
- Guest reviews
- Damage protection
- Security deposit
- Background checks
Fraud Detection
- •ML models: Detection of fake listings and suspicious bookings
- •Risk scoring: Each user and transaction receives a risk score
- •Message scanning: NLP for off-platform payments detection
- •Photo verification: CV to check whether the photo matches reality
Review System
Two-way feedback is the key to trust. Key mechanics:
- •Blind reviews: Both see reviews only after both have written
- •14-day window: Limited time to write a review
- •Response: The host can respond to the review publicly
8High-Level architecture and standard scenarios
Architecture + Scenario Explorer
Discovery and booking paths for a two-sided marketplaceDiscovery Plane (read heavy)
Transaction Plane (consistency first)
It's important to separate search read-path and booking write-path: discovery can be eventually consistent, while booking operations must go through a strict transactional path with locking and payment orchestration.
9Key interview points
✓ Be sure to discuss
- •Geo search: index selection (Geohash vs Quadtree vs S2)
- •Availability: how to synchronize with search
- •Double booking prevention: locking strategy
- •Two-sided marketplace: different UX for guest/host
- •Payment flow: authorization vs capture
💡 Additional topics
- •Smart Pricing ML model
- •Search ranking personalization
- •Photo storage and CDN
- •Internationalization (currencies, languages)
- •Experiences (not just accommodation)
Common interview mistakes
- ✗Forget about the two-way nature of the marketplace (guest + host flows)
- ✗Store availability in search index (changes too often)
- ✗Ignore timezone issues for calendar
- ✗Do not discuss trust & safety for the marketplace