SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6c451fb95aea094d85de74121d686c579d20d5685937423e5e8ee88802d51d05' 
  AND token = 'tKEkTcTTD5nS/mWSIk7MqXd6q9g3U9XxemY9CkbrncI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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