SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55319285dfd526511be53acd07633506649b4d04789048b7744e848a8a5ceb5a' 
  AND token = 'C9NTCsQjQXr9kFXhlM/86w+KKxKGtWlHBBG3MtX7SgU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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