You plan to deploy multiple microservices and need a deployment strategy that allows testing and monitoring changes during a gradual rollout and lets you control the portion of users who receive new releases. Which strategy should you recommend?

Progressive exposure is the correct strategy because it allows for a gradual rollout of new features or versions to a subset of users, enabling testing and monitoring in a production environment before a full release. This minimizes risk and allows for controlled user exposure. A/B testing is used for comparing two versions (A and B) to determine which performs better, not primarily for gradual rollout. Feature toggles (or feature flags) are for turning features on or off without redeploying code, which is a component of progressive exposure but not the overarching strategy itself. Blue/green deployments involve running two identical production environments (blue and green) and switching traffic between them, which is a rapid cutover rather than a gradual exposure.