System Design
Design a Fastag Toll Payment System
Asked by:Amazon
paymentstransactionscachingevent_driven
Problem Overview & Requirements
Design a low-latency, idempotent toll-payment system for vehicle tags, lane decisions, balances, and reconciliation.
Key Pillars: High Availability, Low Latency, Scalability, Fault Tolerance.
Topics & Components: payments, transactions, caching, event_driven.
System Design Breakdown
1. Requirements & Scope
Functional & non-functional requirements, DAU/MAU estimates, read/write throughput.
2. High Level Architecture
API Gateway, Load Balancers, Application Microservices, Caching Layer & Message Queue.
3. Data Model & Storage
SQL vs NoSQL selection, schema design, sharding keys, indexing, and replication strategy.
4. Bottlenecks & Trade-offs
CAP theorem trade-offs, consistency models, rate limiting, and cache invalidation strategies.