Marks & Spencer is gearing up for a significant increase in online sales this shopping season, with online retail buying expected to reach 95% of all purchases by 2040. To deliver the best user experience possible, the company needs to ensure a unified brand experience across all channels, as customers are increasingly knowledgeable about products and often research them before visiting stores. In response, Marks & Spencer has shifted its traditional retail approach to be digital-first, introducing new tech such as agile app development, cloud deployments, and DevOps practices to manage the platform's hundreds of microservices. To personalise customer experiences, retailers need to acquire and act on data, which requires understanding and observing every aspect of the customer journey. Marks & Spencer has implemented observability tools, including refined dashboards and New Relic, to gain a real picture of its customer experience and evolve with customers. These efforts have resulted in significant improvements, such as reducing mean time to resolve (MTTR) by one-third and changing incident management processes, allowing the company to respond quickly to issues and provide better customer service.