Design a large-scale Payment Platform
Last updated: April 24, 2026
Quick Overview
Design a high-throughput payment system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Roblox
System Design
Software Engineer
Roblox
April 24, 2026Software Engineer
Technical Screen
System Design
Hard
8
11
2,972 solved
Design a high-throughput payment system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Roblox 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
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Consistency models and replication
Requirements gathering and capacity estimation
High-level architecture and component design
Partitioning and sharding strategies
Message queues and async processing
Monitoring, logging, and alerting
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 handle schema migrations with zero downtime?
- What would the deployment pipeline look like for this system?
- How would you migrate from a monolithic to a microservices architecture?
Practice a Similar Problem on Codemia
Solve a related problem with our interactive workspace, get AI feedback, and view detailed solutions.
Solve on CodemiaSample Answer
Requirements
Functional Requirements
- User Accounts: Support user account creation and management for both buyers and developers.
- Payment Methods: Allow users to link multiple payment methods (cre...
Capacity Estimation
Back-of-Envelope Calculations
- User Base: Assume 100 million active users with an average of 3 transactions per user per day.
- Transactions: This results in approximately 300 million t...
Submit Your Answer
Markdown supported