Design live sports scores and commentary
PremiumReal-timeEasy
- SSE
- CDN fan out
- Polling vs push
Quick answer
This real-time interview question asks you to design live sports scores and commentary. Aim for a design that delivers updates to many users with low delay, then explain connections, fan-out, ordering and trade-offs. Interviewers want to see how you keep latency low, handle reconnects and stay correct under load.
The problem
Design live sports scores and commentary for a sports app like Cricbuzz or ESPN. Operators enter events (a goal, a wicket, a commentary line) and fans following the match see them within a few seconds; the hard part is a final with 50 million followers, where every goal causes a flood of app opens.
Events come from operators at the ground or a data provider and also include cards, substitutions and corrections. Most fans are idle readers for minutes between events, then all of them want the new score at once.
What must the system do?
- Match state: Each match has a current score, clock or over, and a list of events in order.
- Follow: A fan opens a match screen and sees the current state immediately, then receives updates live.
How well must it do it?
- Latency: An event is visible to fans within 5 seconds of entry; 10 seconds is acceptable for commentary lines.
- Burst tolerance: A goal causes 10 million app opens within 30 seconds; the system must serve them.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- SSE
- CDN fan out
- Polling vs push
- Thundering herd
- Event sourcing
- Idempotent updates
How you’ll practise
- Requirements
- Estimate
- Connections
- Message flow
- Delivery guarantees
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any real-time design round.
- Clarifies latency, ordering and delivery guarantees
- Chooses a connection model with reasons
- Explains fan-out to many receivers
- Handles reconnects, missed messages and duplicates
- Plans for hot spots and sudden traffic spikes
- States trade-offs between consistency and speed
Questions people ask about this interview question
- Which design type is this question?
- It is a real-time question. You design live sports scores and commentary and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Easy, so it suits engineers who are new to real-time interviews. It is also a good warm-up before harder questions.
- What should I cover first?
- Start with who sends and receives updates, how fast they must arrive and what order matters. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team