SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f3b5933ea991dd15b8913f71293717d58393ce6ffe0dcfbe5f4dbb61fed67c8' 
  AND token = 'm6Wb4/pCIjEXkhCbnGTsH/IXX9s9ZrVMMjmUuHmSepc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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