Appendix D. Two-phase commit (2PC)
We discuss two-phase commit (2PC) here as a possible distributed transactions technique, but emphasize that it is unsuitable for distributed services. If we discuss distributed transactions during an interview, we can briefly discuss 2PC as a possibility and also discuss why it should not be used for services. This section will cover this material.
Figure D.1 illustrates a successful 2PC execution. 2PC consists of two phases (hence its name), the prepare phase and the commit phase. The coordinator first sends a prepare request to every database. (We refer to the recipients as databases, but they may also be services or other types of systems.) If every database responds successfully, the coordinator then sends ...
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