SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35b669a433f237754c6fb9387a853cfafcbf109a18be8b748007456b989834bb' 
  AND token = '8vLnafTuLJd1CYtNebHmCnw7aPOaaURKD6ScUMLuI9A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}