SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '312ca0d2ede4b08837526d1697ad8d86be8e71553e51d0940b8a3b620a9eeebd' 
  AND token = 'iU6C/kROJdrRK41LdwD9pM0vj850YuPl1Y3jqfSuy/U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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