From my experience with both HDP and CDH, they are both scalable. Currently, most people in my company have shifted to Azure, so they are using Gen2 primarily and discarding Gen1.  

Hortonworks Data Platform is scalable, but it lacks the capability for horizontal scaling. Therefore, we need to add more servers to increase its capacity.

The product is scalable. It's not a problem if you would like to expand it. 

We have five Hortonworks Data Platform users in our organization. It is a scalable platform.

We expect to have a lot more data. The scalability is the key reason why we are on this platform.  

The solution is very scalable. In our procedure, there are two we are using in production without any downtime. The most important thing is the hardware from the computer cluster. I can work on more than 1,000 servers at the same time. On the communication solution, currently, 50 people use it at the same time.

We have not acquired any additional hardware since our initial purchase. However, we expect more use cases to be added, at which point we may have performance or scalability problems.

Almost every part of the Hadoop ecosystem has its problems and bugs.

No issues encountered.

I have not encountered any scalability issues at all. That's the key reason we picked HDP over Cloudera, as Cloudera have issues & don't support compression of Hive in ORC format. They push only their products (not good).

No issues.

Scalability is superb.

We faced some issues while upgrading to newer versions with current distributions, but with their support we solved it.

No issues with scalability.

Sometimes there were issues.

No, not at all.

No.