BackendDatabasesTable-stakesLegacyAround since 2003
Memcached
A simple, very fast in-memory cache for storing frequently used data so the database isn't hit every time. Redis has largely replaced it for new projects because it does much more.
Think of it like
A sticky note on your monitor with the phone numbers you use most, instead of opening the address book each time.
Junior or senior?
Common at large, older web companies. Fine to see; if a candidate chose it over Redis recently, ask why.
Ask them
“Why Memcached rather than Redis in that system?”