SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6e067a47e6250d27eb8a5b4d1ac47d20a91eef63012a71117796636a8f006efe' 
  AND token = 'sHJU0OaoQ2diJMzrjO4FXt/TIE1si6u8kmnVtUmrojU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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