Caroline Dickey, a Site Reliability Engineer at Mailchimp, shared insights on Chaos Engineering at Chaos Conf 2019, focusing on its application to a monolithic architecture like Mailchimp's, which comprises a significant codebase and primarily relies on PHP. Despite skepticism around monoliths, they remain crucial for Mailchimp's operations, highlighting the importance of ensuring reliability through Chaos Engineering. The approach involves systematically testing infrastructure components, such as load balancers and databases, to validate assumptions about system resilience and identify weaknesses, thereby reducing incident frequency and severity. Dickey emphasized the value of Gamedays—structured exercises aimed at simulating and diagnosing failures to improve system robustness and response strategies. She shared experiences with scenarios like load balancer failover and database read-only modes, which revealed areas for improvement, such as error handling and alerting mechanisms. The presentation underscored the broader applicability of Chaos Engineering beyond monoliths, advocating for its role in enhancing system resilience, fostering knowledge sharing, and building team empathy.