The idea of start-to-end simulation for experiments at advanced light sources, such as x-ray free-electron laser facilities and synchrotron facilities, has been proposed for several years. Such a simulation workflow aims to enable the tracking of x-ray radiation from its source, through the beam transportation to the photon-matter interaction region, and finally, to a photon detector. Several extant software programs simulating different aspects of an experiment have been assembled into the SIMEX platform, which has enabled several insightful works on single-particle imaging. However, the platform’s complicated and sometimes conflicting dependencies have hindered its adoption in other fields, and the scientifically intrinsic complication of each part of the workflow made it challenging for users to optimize all necessary parameters. To address these challenges, we have developed SimEx-Lite, a new core python interface in the SIMEX platform that utilizes optimized templates, personalized back engine installation, new data and parameter classes based on libpyvinyl. This paper introduces the architecture of SimEx-Lite and illustrates its applicability and usefulness in scientific research through selected examples at XFEL facilities.