Friday, 12 August 2011

The Power of Pairs

In my current contract we have a policy of full-time pair programming. It has been working incredibly well. I thought I'd share some of my observations as to why this might be the case.

Previous experience of pairing

I've used and worked with pairs in previous roles with various degrees of success. However, none of those previous roles adopted the full-time pairing model. I've always seen some benefit in pairing, especially on complex or critical pieces of code: two minds working together on these sorts of problems is invaluable. My previous roles have, however, always gone back to singletons for the more mundane and less critical coding tasks.

The one thing I have never seen previously is any of the purported productivity boosts from pair working. This could be because I've only used pairs on for complex tasks, which would take a long time anyway. But surely I should have seen some benefit in the past? Why didn't I?

Our pairing model

The team that I am working with at the moment is made up of five developers. Each of us comes with experience of many successfully completed projects. We all have different language and domain backgrounds, but there seems to be a common thirst from every member of the team for learning and improving. I think this is perhaps one of the key reasons why our pairing model works so well.

Each day we swap the pairs. Sometimes if we are deep in a task we might keep the same pair for two days, but never longer. The dynamic of the team is therefore always changing. It also encourages up to keep tasks small so that we can generally complete them in a single pairing session.

Hold on, don't we have an odd number of people? Yes, and this I think works very well. Each day we pair up and one person gets to work on their own for the day. We try to ensure that each person gets to be the singleton regularly. This single person picks up simple technical debt tasks, carries out investigative spike or just refactors and tidies up the code base. They are requested not to pick up any complex development. Working in pairs is incredibly demanding of concentration and being the singleton for a day also helps keep people fresh.

The benefits

So, why does this pairing model work so well, and why have we created a team that appears to be incredibly productive? Here's my thoughts…

The right team members - All of the developers on the team are good developers and more importantly they are open and keen to learn and improve. We have a number of different language and platform backgrounds on the team, but rather than being a problem it is just more useful information to share between us. The team members have created an environment of sharing and constant learning.

Willingness to question and compromise - Every member of the team has the ability and confidence to question the approach being taken by the other developer in their pair. While I think experience helps in this, you really want even junior team members to have this confidence to question. Linked to this is the fact that each team member is open to new ideas and is either prepared change their thinking or, even if they disagree, come to some form of compromise to allow the pair to continue moving forward. Developers who argue, fail to question or who are not prepared to learn and adapt will kill a pair's productivity.

Shared knowledge - By rotating the pairs on a daily basis, knowledge of the application, language and development approaches is spread throughout the team. This just wouldn't happen if pairs were fixed or people working alone.

The right tools and environment - The team have created a development and build environment that they are comfortable with and that is productive. The team are empowered to make any changes that allow them to work better. These could be changes to the build process or introduction of a new library the cuts the amount of or simplifies code.

A focus on quality - All the members of the team have the same view of the importance of quality and testing. There us a mutual agreement of what constitutes good quality and all team members strive for this goal. Teams where there are differing notions of quality between individual members just don't work as well - even in a non-pairing environment.

The ability to technically invest - By having one team member constantly assigned to cleaning up technical debt, refactoring and improving the code base it allows the pairs to spend all of their time investing in new features. The code base is kept clean and this makes it much easier to introduce new approaches or libraries that further improve the code.


So, would I adopt full-time pair programming again in the future? Definitely! However, to get the real benefit you need the right team of people and you need to create the right environment and culture for them to work in and give them the right set of tools. I'd also try to always have an odd number of developers so that pairs could be rotated and one person be free to clear down any technical debt so that the pairs can invest.


  1. I am wondering if the same level of productivity and goodness can be acheived by pairing with very remote people, does this happen with you currently? Would it actually have the same affect?

  2. I have tried pairing remotely, and I've yet to seem the same benefits as two people around the same machine. There are a few reasons I think it doesn't work quite as well:

    - Tools: there just don't seem to be any really good tools for remote pairing. Mainly we ended up on Skype screen share which always meant one person having laggy screen updates and slow text input. Really need a distributed IDE (*product idea*)

    - Headsets: Maybe I'm just not from the Call of Duty/WoW generation, but I found communicating via a headset to be far less efficient than face-to-face. I think a lot of it is to do with loosing the non-verbal expressions and clues that make up a large part of face-to-face communication.

    - Focus. This is the biggest for me. Sitting next to someone working on the same machine causes you to really focus and reduces distraction. I just wasn't able to get this effect pairing remotely and I think this focus is what makes good pairing so successful.