  Background: Microservices migrations are challenging and expensive projects
with many decisions that need to be made in a multitude of dimensions. Existing
research tends to focus on technical issues and decisions (e.g., how to split
services). Equally important organizational or business issues and their
relations with technical aspects often remain out of scope or on a high level
of abstraction. Aims: In this study, we aim to holistically chart the
decision-making that happens on all dimensions of a migration project towards
microservices (including, but not limited to, the technical dimension). Method:
We investigate 16 different migration cases in a grounded theory interview
study, with 19 participants that recently migrated towards microservices. This
study strongly focuses on the human aspects of a migration, through
stakeholders and their decisions. Results: We identify 3 decision-making
processes consisting of 22decision-points and their alternative options. The
decision-points are related to creating stakeholder engagement and assessing
feasibility, technical implementation, and organizational restructuring.
Conclusions: Our study provides an initial theory of decision-making in
migrations to microservices. It also outfits practitioners with a roadmap of
which decisions they should be prepared to make and at which point in the
migration.
