Design an Event Tracking SDK / Client

Problem

Design the client-side event-tracking SDK that apps use to send analytics events to Amplitude.

Requirements

• track(event, properties); identify(userId, traits)
• Batch and flush events (size/time triggers)
• Retry on network failure; persist unsent events
• Respect opt-out

What evaluators look for

• Clean API; batching and flush policy
• Offline durability and retry/backoff
• Thread safety; minimal app overhead

Extension

Add sampling and a plugin/middleware hook for enriching events.