SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ade4c7e1d26e26f11984ff9fc7bd897fa425c9f730a0b608fce624a666feca4' 
  AND token = 'Lj1wEcFCX5nSJ708y2cAwpfRxAKZCYHrOuDbnKyYT/o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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