SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c163924e65194a9ed04f3bb56c88d002cacd971430fa35c965b548833c033b9b' 
  AND token = 'fIx218I9b+3ClPhdky/X8pAC/UkShTAslaZS90wdO/g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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