In many Agile training programs and conferences, a common question that gets raised is, does Agile/Scrum work in maintenance projects?

I always say "YES" and the team needs to tweak or invent the practices to suit their needs.
Maintenance projects could be enhancement projects OR pure defect fixing projects.

Enhancement projects involve new set of developments over existing one. Since the developers get a new set of requirements at the end of each iteration, one can apply the standard set of Scrum practices with little or no modification.

Defect Fixing projects involve fixing defects on closed or current projects not in development. Sometimes these projects are boring, especially if a new team has been hired for defect fixing purposes only. The customer sends a set of defects on a daily basis or weekly basis with a deadline to deliver. The development team needs to fix them ASAP and send the patch for further testing.

While coaching one of such a defect fixing projects, I found that the following Scrum practices can be applied without much modification:

1. Daily Scrum meetings
2. A Scrum of Scrum
3. Modeling days while solving complex defects
4. Information radiators displaying InProgress, completed, reopened, closed defects and other information
5. Usage of Wiki for collaborating with the customer
6. Requirement workshop while understanding complex defects
7. Review and Retrospective

A common problem that I have found in defect fixing projects is setting the iteration length. Especially if the defects are given on a day to day basis without prior knowledge of what you are going to get, it makes the life of the development team bit difficult.

This can be solved by collaborating with the customer and coming up with a plan to have 1 or 2 weeks of iteration length.