Design a Task Scheduling Service
Last updated: September 6, 2025
Quick Overview
Design a geo-distributed task scheduling system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
ServiceNow
September 6, 20259
13
262 solved
Design a geo-distributed task scheduling system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during Technical Screen at ServiceNow. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. ServiceNow values engineers who can think about scalability from day one.
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 a 10x increase in traffic overnight?
- How would you optimize costs as the system scales?
- How do you ensure data consistency across multiple services?
- What monitoring and alerting would you set up on day one?
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Requirements
- Functional Requirements:
- Create, update, and delete tasks with scheduling options (immediate, delayed, recurring).
- Support geo-distributed task execution across multiple regions. ...
Capacity Estimation
- Request Volume: Assume 10 million tasks submitted daily, averaging around 115 tasks per second (QPS).
- Data Storage Needs:
- Each task contains metadata (task ID, type, status, timest...
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