SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c2a64a14a069e957d4f125bbd1dba03149be0335b15566d79e17e0d2a0cc6cb' 
  AND token = 'h68WQo8JZWItc8HoOsTHTN+7SrchLEg6XbO+msGeK28=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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