Designing for Failure to Avoid Disaster

LaunchDarkly is a reliable service that prioritizes availability and correctness. Over 40 billion feature flags are evaluated daily on the platform, ensuring customers can depend on it. The company has worked hard to create a robust service against various types of failures over the last four years. LaunchDarkly SDKs streamline integration by fetching all feature flags and evaluation rules automatically when an application starts. Flags and evaluation rules are cached locally in applications, reducing performance overhead. In case of failure or worst-case scenarios, the platform ensures that applications continue to perform as expected using locally cached values. LaunchDarkly also offers LD-Relay for additional redundancy, which can be deployed in a customer's environment and uses an optional Redis cache for storing flag evaluation rules. The streaming connections provided by LaunchDarkly ensure fast and reliable delivery of updates to flag or evaluation rules across all connected SDKs. This is crucial for microservice architectures and distributed systems that require consistent application of rules.