SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9b046a5b71195a20d5a3806f3f427aba1f7c0be1a31fd748171c960835e52b4' 
  AND token = 'XtTYtfib0rzUphnYKd8m8YBbdcvZTCcfFSnmKbt1McM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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