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.

What difficulty level is this interview question?

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

What role is this question designed for?

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

Design a scalable Instagram-like platform | DoorDash Interview Question

Quick Overview

This question evaluates a candidate's ability to design a scalable, read-heavy social media backend encompassing media ingestion and storage, personalized feed generation, data modeling, sharding, consistency vs availability trade-offs, observability, and cost/DR planning, testing competencies in distributed systems, performance engineering, and operational design. Commonly asked in system design interviews to assess architectural reasoning and trade-off analysis, it is categorized under System Design and requires both high-level conceptual thinking and practical application details such as APIs, data models, capacity estimates, and component-level considerations.

Context

Design a photo/video sharing platform with core social features and a personalized feed. Optimize for large-scale read-heavy workloads and mobile clients. Optional features (stories, DMs) may be stubbed but need not be fully designed.

Requirements

Core features
- User sign-up/login, follow/unfollow
- Upload photos/videos
- Personalized home feed
- Likes, comments
- Notifications
- Search (users, hashtags, captions)
- Optional: stories, direct messages (outline only)
Deliverables
- Public APIs (CRUD and feed endpoints)
- Data models and key indexes
- High-level architecture and components
- Media ingestion pipeline: upload, storage, thumbnailing/transcoding, CDN delivery
- Feed generation and ranking: pull vs push, fan-out strategies, timelines, caching, handling hot accounts
- Consistency vs availability trade-offs
- Sharding/partitioning strategy and read/write scaling
- Privacy and access control
- Abuse/spam mitigation
- Observability (metrics, logging, tracing)
- Cost controls
- Multi-region disaster recovery
- Back-of-the-envelope capacity estimates
- Evolution plan from MVP to planet scale

Design a scalable Instagram-like platform

Quick Overview

Context

Requirements

Solution

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Design a scalable Instagram-like platform

Quick Overview