Deep dive a project's architecture

Q: Deep dive a project's architecture

This question evaluates a candidate's ability to design and articulate end-to-end system architecture, including components, data flow, scalability, reliability, security, observability, and operational trade-offs, thereby assessing architectural thinking, system ownership, and technical justification skills.

Q: How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

Q: What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Technical Screen rounds at DoorDash.

Q: What role is this question designed for?

This question is commonly asked for Software Engineer candidates at DoorDash during technical interviews.

Question

System Design Deep Dive: Past Project

Provide a deep dive on one production project you owned or co-built. Assume the audience has not seen your system before. You may anonymize proprietary details. ASCII diagrams are acceptable.

Deliverables

Architecture diagram
- Components, data stores, and interfaces (APIs, events, contracts).
Data flow and key invariants
- End-to-end request/event flow; call out the invariants that must always hold.
Technology choices
- Justify major choices and trade-offs.
Scalability and performance
- Expected load, bottlenecks, and how you scale horizontally/vertically.
Consistency and reliability
- Consistency model, failure handling, retries, idempotency, backpressure.
Security and access control
- Authentication, authorization, secrets, encryption.
Observability
- Logs, metrics, traces, alerting, and top SLIs.
SLAs/SLOs
- Target latencies, availability, and error budgets.
Incident or trade-off
- A significant incident or trade-off you handled, with root cause and remediation.
Redesign

What you would change today and why.

Tip: Be concrete with APIs, schemas, and SLOs; highlight the risks you mitigated and the ones you consciously accepted.

Deep dive a project's architecture

Quick Overview

System Design Deep Dive: Past Project

Deliverables

Solution

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