SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c43f823ab38052969920bdf99a3f80282568a9384bcf683d5f43b60ff907e64f' 
  AND token = '68udQYGg2sgWYRmG+bqImiS/wxAFRMRM0N5ixtzgMsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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