SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb4441bc2ff8e9aa808d7ed20036d75b57f5a3e6b7e86955fcad75ce3d9db551' 
  AND token = 'KzOMUqXEK8QBkl4NtUfHuiJx6JD4ZqitFq/QzVxVAHQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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