framework, gRPC, 2021, https://grpc.io/ . • Protocol Buffers, Google, 2021, https://developers.google.com/protocol-buffers . • gRPC vs REST: Understanding gRPC, OpenAPI and REST and when to use them in API design, Google, 2020 . https://cloud.google.com/blog/ja/products/api-management/ understanding-grpc-openapi-and-rest-and-when-to-use-them • Rodrigo Quezada, GraphQL & gRPC, 2017, https://blog.datank.ai/graphql-grpc-part-1-54d92a109619 • Andrew S. Tanenbaum, 分散システム--原理とパラダイム, PEARSON, 2009.