Design a Zap (Trigger -> Actions) Engine

Problem

Design Zapier's core abstraction: a Zap = a trigger plus an ordered chain of actions with data mapping between steps.

Requirements

• Trigger fires with a payload
• Steps run in order; each maps fields from prior steps
• Filters/branches; error handling and retries
• Pluggable app integrations

What evaluators look for

• Clean model: Trigger, Step/Action, Zap, RunContext
• Field mapping between steps
• Retry/idempotency for side effects

Extension

Add a fan-out step (one trigger -> many items) and per-item runs.