Deep Technical Review of a Recent System

Context: You are interviewing for a system design/engineering role. Select one substantial project you worked on and present a deep technical review that another senior engineer could evaluate without prior context.

Deliverables:

1. End-to-end architecture

• Provide an ASCII architecture diagram.
• Enumerate core components and their responsibilities.
• Describe synchronous and asynchronous data flows.

2. Read and write paths

• Walk through the end-to-end read path(s) and write path(s).
• Include latency budgets and failure handling.

3. Data and storage

• Schema design (entities, keys, indexes, partition/shard keys).
• Storage technology choices and why (including alternatives considered).

4. Design decisions and trade-offs

• Call out at least 5 key decisions and the trade-offs (e.g., consistency vs. availability, latency vs. cost, operational simplicity vs. feature set).

5. Scaling and capacity

• State current scaling limits and bottlenecks.
• Provide a back-of-the-envelope capacity plan (QPS, throughput, storage growth, partition counts).

6. Reliability and security

• Fault tolerance: failure modes, retries, backpressure, DLQs, circuit breakers, multi-AZ/region.
• Security/compliance: authN/Z, transport and data-at-rest encryption, PII handling, audit/retention.

7. Operational readiness

• Dashboards, SLIs/SLOs, alerts and thresholds.
• Runbooks and on-call procedures.

8. 10× traffic plan

• Propose two concrete improvements for a 10× traffic increase and justify each with expected impact and risks.