Tier 1 services are critical to a company’s profitability. They address the primary use cases for the organization’s products or support its underlying vital infrastructures, such as a product search service for an e-commerce site, a content posting service for a social media app, or a payment processing framework. Building a robust Tier 1 service, either a front-facing platform that powers customers' experience or the backend services behind that platform, is crucial to driving a positive customer journey.
Tier 1 services should be resilient to outages because availability issues can lead to mistrust and dissatisfied customers. A bad encounter with a website or an app that locks up or is painfully slow (latency), especially when there are other options in the same business sector, can spell disaster for the company behind the service. That is why it is important to build these services right the first time.