As  Atlas Proxy would send tenant token with "expectPrefix: true" on every request before we rolled out mongoq, that means we only parse tenant id from database strings when "expectPrefix:true" is set in the unsigned security token. We need to remove support for parsing tenant id from prefix of database strings without "expectPrefix: true".

For example, if we receive a request {count: ..., $db: tenantA_myDb} without security token, we should return error instead of counting documents of the tenant db with DatabaseName(tenantA, myDb).