Availability
Availability is a core concept in system design and reliability engineering that measures the proportion of time a system or service is operational and accessible to users. It is often expressed as a percentage (e.g., 99.9% uptime) and is a key component of service-level agreements (SLAs). High availability ensures that systems can withstand failures and minimize downtime, which is critical for applications requiring continuous operation, such as e-commerce platforms or financial services.
Developers should learn about availability to design resilient systems that meet business requirements and user expectations, especially for mission-critical applications where downtime leads to revenue loss or safety risks. It is essential in cloud computing, distributed systems, and DevOps practices, where techniques like redundancy, load balancing, and failover mechanisms are used to achieve high availability. Understanding availability helps in making trade-offs with other system properties like consistency and partition tolerance, as per the CAP theorem.