Coach Tony has provided the following feedback on your session:

Pradeep demonstrated strong technical depth and ownership throughout the system design session. His approach reflected solid Staff-level thinking with room to sharpen a few key Staff+ dimensions.

Areas of strength included:

• Thorough API and FR/NFR coverage: Presented a well-scoped list of functional requirements with corresponding APIs (e.g., putFile, createDirectory), and proactively framed non-functional goals, including consistency, scalability, and latency expectations.
• Clear architectural breakdown: Organized the system into clean layers (metadata, chunk storage, read/write services) and aligned each with functional flows using a visual color-coded explanation.
• Scalability and sharding awareness: Identified hotkey risks and discussed initial mitigation (e.g., ads_id sharding, region-awareness).
• Distributed coordination experience: Brought in practical experience with Zookeeper to model locking strategies and hinted at scale-sensitive branching of those designs.
• Caching strategy: Proposed an L1 cache for chunk reads and metadata for low-latency access paths.
• Effective communication: Proactively checked alignment throughout the session and clearly narrated trade-offs.

Areas for improvement:

• System primitives: Consider listing foundational primitives and components you would leverage—e.g., object stores, Raft/ZAB, quorum reads, content-addressed storage.
• Multi-tenant design: Add assumptions and design considerations for regional isolation or tenant-specific scaling—especially for enterprise-scale file systems.
• deleteDirectory() logic: Rather than scanning arrays of children, think in terms of residual counters for performance and correctness. Also surface garbage collection implications when files are marked for deletion.
• Consistency trade-offs: Good mention of Zookeeper, but dig deeper into latency vs coordination cost—quantify when locks are necessary and explore alternative patterns (e.g., CRDTs, version vectors).
• Hot-key mitigation: Consider expanding into concrete strategies such as:
  • Hashing directory names
  • Bucketing at the application level
  • Pagination + lazy materialization

Take-Home Questions

To reinforce your Staff+ readiness, consider reflecting on these:

1. Block Hashing: How exactly is block_hash computed? What happens with collisions or variable chunk content?
2. Garbage Collection: After file deletions, what mechanism ensures orphaned chunks are cleaned up?
3. Cost Efficiency: How would you reduce storage costs in cold vs. hot tiers while maintaining latency guarantees?