SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a19ee466f58198600a99232be60877484ee073f018235d8e4baa8ded5ce38b3f' 
  AND token = 'lQrZs/sObj913evj4qGfAHZQBpybBTFZhe37KGHqB6A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}