SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '08515a95d5b51243c4fe37d40f5f0dba06709928c2e203abac36fa9654b956da' 
  AND token = 'xJAY0zUMBN0kxDSue4U73iLjCfMYxUibrgt9yri0bMI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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