SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9a8afb251baf8a2e7b6ce75d54129dfcd12fa8d2f295f0439e956ddcd3b5fbe7' 
  AND token = 'aNwTn6TQmaLm/cS6tAIPTSuMSn2XBcHajNgtKVjFLt0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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