Discuss queues, NoSQL, and concurrency
Overview
This question evaluates understanding of distributed messaging systems, delivery semantics, push versus pull consumption models, NoSQL versus relational storage trade-offs, and concurrency control including deadlock concepts.
System Design Concepts: Messaging, Storage Choices, and Concurrency
Context: You are designing distributed services that communicate via events and must handle bursty traffic, data storage trade-offs, and concurrency challenges.
1) Message Queues
Explain the role of message queues in:
- Decoupling producers and consumers
- Smoothing traffic spikes (load leveling)
2) Delivery Semantics
Define delivery semantics and describe how to achieve each in practice:
- At-least-once
- At-most-once
- Exactly-once
3) Push vs. Pull Consumption
Compare push vs. pull event delivery models. Discuss trade-offs for:
- Latency
- Throughput
- Backpressure
- Client complexity
4) Storage Choice: NoSQL vs. Relational
When would you choose a NoSQL datastore over a relational database? Discuss:
- Data models
- Consistency models
- Scaling
- Query patterns
5) Deadlocks
Define a deadlock in concurrent or distributed systems and outline techniques to prevent, avoid, detect, and recover from it.
Solution
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