This article examines the relationship between Key Performance Indicators (KPI) and results in e-commerce, highlighting metrics such as conversion rate, customer life cycle and profitability of digital marketing campaigns. Strategies are explored to improve the performance of online sales and promote sustainable practices in e-commerce, with a focus on adapting these indicators to the Portuguese market. The selected methodology includes a bibliographical review, including contributions of several articles to relevant authors, together with an empirical analysis of data provided by sources such as EUROSTAT and ANACOM. After analyzing the selected bibliography, it was possible to verify that KPIs are one of the most influential tools in achieving competitive advantage for e-commerce companies. The correct application of KPIs will depend on their context and applicability, which makes it imperative to determine implementation and monitoring timings.