This is the top layer of the cache hierarchy - it keeps as many coins in memory as can fit per the dbcache setting.
Declared in <validation.h>
[[guarded_by(0x7fbc8fa68bc8), guarded_by(0x7fbc96b010d8), guarded_by(0x7fbc84657c48), guarded_by(0x7fbc9e00fec8)]]
std::unique_ptr<CCoinsViewCache> m_cacheview;