This book constitutes the refereed post-conference proceedings of the 11th and the 12th International Conference on Big Data Technologies and Applications, BDTA 2021 and BDTA 2022, held in December 2021 and 2022. Due to COVID-19 pandemic both conferences were held virtually. The 23 full papers of BDTA 2021 and BDTA 2022 were selected from 61 submissions and present all big data technologies, such as big data collection and storage, big data management and retrieval, big data mining approaches, big data visualization, and new domains and novel applications related to these technologies.