SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db4619f0de9122d6baa8ba68c401d5939eef323bc109d3d70f0c6f164685feae' 
  AND token = '35lD1E0QjBNvRS/++6nGILxzlscXo9hnu9KlfwZu7Jg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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