SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c40f808763fa9d02ecbe3547b17eb3d1d7140adb1e55fbd38d6be9721f62d355' 
  AND token = 'x2sOFUXSUE+7zCyU9LvCOIOfRpCN/DZwcbK+Hj/+IXg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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