With the rapid growth of instant delivery services in China, the number of couriers is rising due to low entry barriers such as minimal educational requirements, flexible hours, and competitive salaries. However, the industry faces challenges like excessive workloads and high accident rates, which could reduce couriers' job satisfaction. While the literature on couriers' job satisfaction is extensive, the application of holistic needs-based theories remains unexplored, particularly through advanced quantitative methods. This study operationalizes Maslow's Hierarchy of Needs Theory (MHNT) as a multi-dimensional construct and incorporates it into a Structural Equation Modeling (SEM) framework to examine its hierarchical impact on job satisfaction. Additionally, it explores the impact of physical health, occupational discrimination, and new technologies on couriers' job satisfaction. To test the framework and derive a nuanced understanding of factors influencing courier job satisfaction, data from 490 couriers in Shanghai, China, and nearby areas was collected. To account for differences in employment types, the survey data was split into full-time and part-time courier groups, with a multigroup analysis conducted using a structural equation model. The results show differing factors influencing job satisfaction. Part-time couriers are significantly affected by compensation and working environment, while full-time couriers are, besides compensation and working environment, also influenced by career development. These findings enhance the understanding of work conditions and motivators for couriers across different employment types within the instant delivery sector, offering key insights to enhance courier job satisfaction and promote sustainable development of this business.