Twitter At Scale: Will It Work?

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Only two days ago the contact messaging application Twitter suffered another bout of downtime, leaving some users frustrated and others asking why the platform continues to suffer problems.

I have recently spoken to an individual who is familiar with the technical problems at Twitter as well as the challenges that lay ahead for the startup. He re-iterated his belief that the problems lay not with Blaine Cook (the former head of engineering who was shown the door), nor with Joyent NTT (their host) but with the early lack of understanding of how complex their problems would be.

The issue is that group messaging is very difficult to achieve at a grand scale. Other large sites such as WordPress and Digg are mostly dealing with known problems, such as how to serve a large number of pages or a large number of images. Twitter is unique in that it needs to parse a large number of messages and deliver them to multiple recipients, with each user having unique connections to other users.

Social networks have similar complexity issues, but they only usually need to route a message to a single user (or at the most to a defined group). Even so, social networks like Friendster struggled for years with technical and scaling issues. Twitter is specifically dealing with text messages, and in most cases with active users those messages are very frequent and go out to hundreds of contacts (or followers, as they are referred to in Twitter). Every new Twitter user and every new connection results in an exponentially greater computational requirement.

Some of the best web applications are able to efficiently solve very complex problems to produce simple results for users (Eg. Google). The success of these applications is due to the innovative efforts by developers to solve large technical challenges, where they have often had to break new ground for solutions. For Twitter to reach a similar point of reliability they too will need a very comprehensive, ground-breaking solution.

The source that I spoke to also commented on how ill-prepared the Twitter team were and are for their current and future challenges. The small team contains a handful of engineers, with only a person or two committed to infrastructure and architecture. He goes on to point out that at Digg the team for network and systems alone is bigger than the total engineering team at Twitter, and that at Digg they are lead by well-known “A-list rockstars”.

The problems at Twitter are often attributed to their use of RubyOnRails, a web development framework. Twitter is almost certainly the largest site running on Rails, so fans of the framework and its developers have been quick to deflect the criticism and point it back at the engineers at Twitter. Utilizing a framework that has never conquered large-scale territory must certainly add to the risk and work required to find a solution. As an out-of-the box framework, Rails certainly doesn’t lend itself to large-scale application development, but was a big part of the reason why Twitter could experiment and release early.

Rails has enabled Twitter to prototype quickly, to quickly launch and then to easily iterate with new features. But the old adage of “Good, Fast, Cheap – pick two” certainly applies; and Rails would do itself no harm by conceding that it isn’t a platform that can compete with Java or C when it comes to intensive tasks. Twitter is at a cross-roads as an application and Rails has served its purpose very well to date, but you are unlikely to see a computational cluster built with Ruby at Apache any time soon.

What we see at Twitter today is a very useful and popular service, but one with very complex underlying technical challenges to overcome. Twitter will require not only a new architecture approach and a big injection of the best minds they can find ($15 million can help), but will also need a little patience from users and those of us observing.

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