SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a40561ef850960cab272c9c7984816a6fe297714e729a6dd23167b4e3f0f9a23' 
  AND token = 'E2ckUprBE5i+LGDAJlwWqInuFkOaR2vsr+dGx7VwQzE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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