Design a ride-hailing service

Hard50 minFree, no account

Geospatial indexing, a matching problem, and state that changes every four seconds.

The question

Design the core of Uber: a rider requests a ride, a nearby driver is matched, and both track the trip.

Drivers report their location every four seconds whether or not they have a passenger.

Functional

Drivers publish location continuously.
A rider requests a ride from A to B and is matched with one driver.
Both see the other's live position during the trip.
Fare calculated at the end.

Non-functional

5M active drivers; location every 4s → ~1.2M writes/sec.
Match within a few seconds.
One driver is never assigned two rides.
Location data is useless after a few seconds.

50:00Commit to an answer before you open the solution. Reading it first teaches you to recognise good answers, which is not the skill being tested.

Stuck?

0 of 3 hints taken

The worked solution

written by a person · not a grade

Score yourself

0 of 5 marked

Separated ephemeral location from durable trip state and justified it25
Named a geospatial index, handled neighbour cells and density skew25
Offered rather than assigned, with a deadline and a fallback20
Closed the two-riders-one-driver race atomically20
Switched to a direct channel once the trip started10

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