We believe it is definitely a Sedum (often called stonecrop). It is often used as a ground cover and sometimes in containers. Following are two NC State University sites which give more infoamriton about Sedums.
This particular plant may be Sedum sieboldii. See this link for more information. https://plants.ces.ncsu.edu/plants/all/sedum-sieboldii/
One characteristic used to identify different species of Sedum is flower color so that may help you find the species if you con't think it is sieboldii.