Small and medium enterprises (SMEs) generate 90% of employment and contribute more than 50% to the world product, where e-commerce (EC) is fundamental to their development. In this study, a systematic review of literature from indexed journals in Scopus and Web of Science is conducted, 73 primary studies are identified to answer the inquiry: What affects EC performance and how is it measured? Twenty-eight definitions for EC, 70 ways of understanding performance in three perspectives (financial, customer-market, and process), 51 metrics to measure them, and 74 factors that affect these were identified. However, there is a lack of studies on performance factors from its process as well as the metrics that contemplate other perspectives, such as technological innovation, social responsibility, and value co-creation. Additionally, studies on factors are oriented to the result but not to the process that generates said result, which means there is a gap to be studied.