High Availability Architecture: Core Concepts

High availability is not a single technology but a mindset of removing single points of failure. Understanding the core concepts is what lets you design systems that keep running through failures.

The ideas are redundancy, failover, and monitoring, working together so that no one component can take the system down. Each layer of the stack needs the same treatment.

• Redundancy means every critical component has a spare
• Failover switches traffic automatically on failure
• Health checks detect failures before users do
• Aim for nines that match your actual cost of downtime

Design each layer to survive the loss of one component, then test the failover paths.