SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8ed7c68556ad5050bfe1fc713b90bde7dd5845adf3ce943d6d0091bcf4f2ddc4' 
  AND token = 'e80uAhVFMj+99DojS5ZqiJ1vym0rRa9ojfhtbefdU+8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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