I have been working on some portals and very big community sites such as Bounty Ltd. In this web site users can post comments, upload pictures, enter competition.
Managing a community of many users required to handle all the user permissions very accurately so that each user is allowed to do only the right operations on each piece of content.
1. Marketing
Drupal 8 has got a robust built-in and secure user registration system. Collect customer information, user preferences to make a unique user journey.
2. Open Source
Scalable, efficient, highly performing and SEO friendly Dupal CMS. Our Government Intranet project has got more than 50,000 registered users.
3. Keywords
Read our article on how to use and configure Drupal to use Simple XML sitemap, Meta Tags, Keywords, ALT and titles on images.
4. Custom
If you cannot find a module that does exactly what you need then need to write a custom module. First try to find the same functionality..