Using a pre-built video transcoding solution

A lot of cloud providers, particularly CDN providers, offer some form of video streaming service, that takes care of transcoding and serving videos for you. These can seem like easy, convenient solutions - which to be fair, they are - but they have specific advantages and disadvantages, and you should consider carefully if they suit your use case.

Advantages

Ease of deployment

Since you don't have to do any development, getting your site to support user uploaded videos (or other video content) is a lot faster and easier using a pre-built solution. 

Low likelihood of bugs

When making your own transcoding solution, there's always the risk of having weird bugs here and there. The pre-built solutions are generally designed by large teams, and have many different customers, so they're going to have been rigorously tested and will be unlikely to give you much trouble in terms of bugs or errors.

Can be a lot cheaper than a dedicated transcoding service

Some providers have fairly cheap offerings, and/or do not charge you for video transcoding and instead only charge for storage and CDN bandwidth, which is a major cost reduction for most use cases (the only time it wouldn't be a cost saving is if you plan on having very few video transcoding tasks, but for videos to be viewed in huge numbers).

Disadvantages

Lack of configuration choices and control, lower quality

Depending on your use case, a pre-built video transcoding solution might not have the options you need it to have (for instance, it might only support a certain set of resolutions and not any others).

In addition, many prebuilt solutions don't give you that much control over how videos are transcoded. This can be problematic if you need videos to be to a particular quality standard, or you want them to be small in filesize but not low in quality, neither of which prebuilt solutions are generally aimed at.

Can be more costly in the long run in some use cases

As most prebuilt solutions don't let you customise the encoding or other options too much, you'll often end up with videos that are larger in filesize than they could be, resulting in higher bandwidth costs.

In many cases, this isn't likely to be a big enough difference to make expensive transcoding worthwhile, but if you're only teanscoding small numbers of videos and expecting very large view counts, it can be worth using a dedicated transcoding service to obtain smaller videos for the same quality and thus reduce the bandwidth costs.