Design a multi-tenant Task Scheduling System
Last updated: September 15, 2025
Quick Overview
Design a multi-tenant task scheduling system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Instacart
September 15, 202534
3
3,569 solved
Design a multi-tenant task scheduling system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Instacart typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
What the Interviewer Expects
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How would you handle schema migrations with zero downtime?
- How do you ensure data consistency across multiple services?
- How would you implement rate limiting to protect the system?
- What happens if one of your database nodes goes down?
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Requirements
Functional Requirements:
- Multi-tenancy Support: Each tenant (e.g., different grocery stores) should be able to schedule tasks independently.
- Task Creation and Management: Tenants sho...
Capacity Estimation
Assuming Instacart has around 500 grocery stores using the task scheduling system, with each store scheduling an average of 100 tasks per day:
- Daily Tasks: 500 stores * 100 tasks = 50,000 task...
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