SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '407280802fc561a9a25b2d50c38af9568a905390bb741b5c0feacdcf8dde3a89' 
  AND token = '4HKY2lcppjA6hLR16HK8W0sVKvFunskrBPOw/idoJOU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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