Daniel demonstrated clear structure, strong breadth across requirements, and thoughtful trade-off discussions. Timing and communication were well-managed, and he connected architectural choices to scalability and reliability concerns.

Areas of Strength

• Clearly enumerated all functional requirements.
  
  
• Defined non-functional requirements with concrete, measurable metrics.
  
  
• Proposed high level working solutions to meet most of high level function requirements.
  
  

Areas for Improvement

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Focus on Staff vs Senior evaluation rubrics and be more proactive propose ideas and align with interviews:

Scope:

• Senior: Designs a single scheduling service (store jobs → run on time).
• Staff: Designs a multi-tenant scheduling platform (millions of jobs, cross-region, fault isolation, SLAs).

Technical Depth:

• Senior: Uses DB + queue + worker polling every few seconds.
• Staff: Uses sharded time wheels, adaptive batching, per-tenant throttling, and exactly-once job execution.

Reliability & Operations:

• Senior: Adds retries and DLQs.
• Staff: Adds observability (lag metrics, alerting), circuit breakers, watchdogs, and cross-region recovery.

Evolution & Ambiguity:

• Senior: Adds recurring jobs later.
• Staff: Plans versioned APIs, migration strategy, and feature-flag rollouts for new schedule types (cron, DAG).

Communication & Tradeoffs:

• Senior: Focuses on correctness and scalability.

Staff: Quantifies tradeoffs (latency vs cost vs accuracy), aligns with org SLAs, and explains long-term platform leverage.