It's a big step to go from having an idea to building a product. Somewhere during the building process, analytics gets added (in reality, usually thrown in). Having a plan about what to track and how is essential in quantifying the success of your product. It should be taken into consideration as early in the building process as possible.
There are hundreds of services that do this measuring and tracking of user actions. Sites can be integrated with a wide variety of third-party services: from analytics tracking (like Google and Heap) to CRMs (like Salesforce) to advertising (like Facebook Pixel and AdWords). Usually the website sends each of these services the data it needs in the format it requires.
Your analytics data is siloed into one service (or more) and user data into others. One service provides an Excel dump of data, another a custom report. This makes it increasingly difficult to analyze the data so you can come to data-driven decisions about what changes to make to better serve your users.
Enter Customer Data Platforms (CDP) like Segment and Treasure Data. These services provide a centralized hub that all the data can be sent to. The platform then sends the data to the eager analytics, helpdesk or other third-party service. All this data can also be stored in a warehouse. The CDP provides tools to query the data. You may not have a solid plan for how you want to use all your data right now, but collecting the data is the first step.
Customer Data Platforms aren't necessary for all sites. They are a better fit for sites that for example want to grow their userbase or increase conversions like buying a product or signing up for a newsletter. There is a cost to these services. Segment offers smaller plans that scale up. Treasure Data is more robust and offers more options when it comes to security, but it's also a lot more expensive.
We recently setup Segment on a site and found it easy to configure add integrations. But of course that is just the beginning. The hard work is in mining the collected data for useful information.
Whether or not you choose to use a CDP for your website or product, consider a tracking plan early. The potential for powerful insights greatly increases when all your data is in one place. It allows you to parse the data and get a complete, single view of a customer. It paves the way for predictive analytics and personalized content. And all in real-time. But it should be a solution that fits the needs and size of the site.