SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef6c4439bd12bc9676c6e174b217dfee3e967d3a3a23ae64a482172d5fc32494' 
  AND token = 'Sqn7ydVwHOTD6LjzXhPZd3YzgCzkNiBSiGTXeKuHmf0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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