  We are recently witnessing an increased adoption of microservice
architectures by the industry for achieving scalability by functional
decomposition, fault-tolerance by deployment of small and independent services,
and polyglot persistence by the adoption of different database technologies
specific to the needs of each service. Despite the accelerating industrial
adoption and the extensive research on microservices, there is a lack of
thorough investigation on the state of the practice and the major challenges
faced by practitioners with regard to data management. To bridge this gap, this
paper presents a detailed investigation of data management in microservices.
Our exploratory study is based on the following methodology: we conducted a
systematic literature review of articles reporting the adoption of
microservices in industry, where more than 300 articles were filtered down to
11 representative studies; we analyzed a set of 9 popular open-source
microservice-based applications, selected out of more than 20 open-source
projects; furthermore, to strengthen our evidence, we conducted an online
survey that we then used to cross-validate the findings of the previous steps
with the perceptions and experiences of over 120 practitioners and researchers.
Through this process, we were able to categorize the state of practice and
reveal several principled challenges that cannot be solved by software
engineering practices, but rather need system-level support to alleviate the
burden of practitioners. Based on the observations we also identified a series
of research directions to achieve this goal. Fundamentally, novel database
systems and data management tools that support isolation for microservices,
which include fault isolation, performance isolation, data ownership, and
independent schema evolution across microservices must be built to address the
needs of this growing architectural style.
