Problem Statement: Consider a system whose state is partitioned by design into read-only state, ACID state, session state, and volatile runtime state. The application logic obeys all requirements for being microrebootable. Assume the read-only state goes into a file system mounted read-only, and ACID state goes into a transactional database with an SQL interface. Design an interface for the session state store, obeying all rules for keeping the system microrebootable as well as all principles for good system design we've seen so far in POCS. The system can experience both reboot-curable failures as well as non-reboot-curable ones. If it makes things easier, you may assume that the system is an e-commerce site like eBay, subject to customary requirements. Describe the interface using a real programming language (e.g., in the style of a simple C header file or a Java interface) or easily understandable pseudocode, along with suitable code comments. Please do not use any prose in this OP, just let the code do the talking. You may use a maximum of 3,000 non-whitespace characters. Submit your OP as a file that conforms to the ISO 32000-1 PDF 1.7 standard.
Interesting solutions (neither of these is perfect, but each one offers something notable):