System Design

What does Chime expect you to consider under reliability?

• Retries

• Handling data loss

  • Component failure tolerance

What does availability mean in Chime’s rubric?

• System should stay up and responsive

• Use load balancing to route traffic across instances

What is Chime looking for when they mention exception handling?

• How you gracefully handle errors and failures

• Avoid crashes or user-facing disruptions

Why does Chime want you to consider logging and alerting?

• Logging: track system behavior and events

• Alerting: notify engineers when something breaks

What does Chime mean by horizontal scalability?

• Add more machines to scale out

• Useful for read-heavy or write-heavy systems under high load

When should you choose asynchronous processing at Chime?

• To reduce latency for the user

• When the operation doesn’t need to be immediate (e.g. check deposit backend confirmation)

How does caching help in Chime’s system design expectations?

• Reduce latency or repeated reads

• Offload database pressure

What is data redundancy, and why does Chime care?

• Duplicate important data across regions or services

• Helps with durability and disaster recovery

What is meant by capacity planning in a Chime interview?

Estimate system needs (RPS, data size, traffic spikes)

What’s the difference between synchronous and asynchronous processing?

Synchronous: caller waits for the result (e.g. login auth)

Asynchronous: caller doesn’t wait - result handled later (e.g. email send, background job)

When should you use asynchronous processing in system design?

• For long-running or non-urgent tasks

• To reduce latency for the user

• To decouple components and improve system resilience

How do you implement data redundancy in system design?

• Primary + replica databases

• Cross-region replication

• Event logs + eventual consistency

• Cloud provider redundancy (e.g., AWS multi-AZ)

What inputs do you need for capacity planning?

• Expected daily/monthly active users

• Read/write request ratio

• Peak vs average traffic

• Latency requirements

• Headroom for spikes

Why is capacity planning important?

• Prevents bottlenecks and downtime

• Ensures components are correctly sized

• Guides autoscaling and resource allocation