In my time at Samsung, we were tracking most of the authoritative state for the factory in a single monster Oracle DB instance. This made troubleshooting systems integration problems fairly trivial once you had some business keys to look for.

There are so many crazy tricks out there. You would be amazed at how much abuse an old school RDBMS engine can take on modern hardware. In-memory OLTP on servers that can host terabytes of RAM completely changes the game. Disaggregated compute & storage provides seamless OLAP capabilities on the same SQL connection instance for the most modern providers.

Oracle (the software) isn't a database, though. It is a database management system. It seems highly unlikely that it kept all the data in one place. Different workloads generally need different database structures. And Amazon circa 2008 was complex enough that it no doubt had a gamut of different workload needs, even if that was all managed under one management system.

Really, as it pertains to this, it is a question of "where do I want to move the complexity to?", not "can I eliminate it?"

There were no derivative stores (Redis caches? Solr views?) around it?