Consistency vs Availability

Quick Reference: Push vs Pull | Step 3: CAP Theorem

Quick Reference

Consistency: All nodes see same data

Availability: System remains operational

Trade-off: In distributed systems, prioritize one during partitions

Clear Definition

Consistency vs Availability is the fundamental CAP theorem trade-off. During network partitions, choose consistency (CP) or availability (AP) based on requirements.

šŸ’” Key Insight: Financial systems = consistency, social media = availability. Most systems use hybrid approach.

Core Concepts

CP Systems

  • Prioritize consistency
  • May reject requests during partition
  • Examples: MongoDB, HBase

AP Systems

  • Prioritize availability
  • May serve stale data
  • Examples: Cassandra, DynamoDB

Best Practices

  1. Understand Requirements: What's more important?
  2. Hybrid: Different consistency for different data
  3. Monitor: Track consistency and availability

Quick Reference Summary

Consistency: All nodes see same data. Critical for financial systems.

Availability: System stays operational. Critical for user-facing apps.

Key: Choose based on requirements. Many systems use hybrid.

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