Backlog

A backlog is a list of things that still need to be done. The English word literally means something like “a build-up of unfinished work.” In teams that develop software or products, it contains everything one could wish for the product: new features, improvements, reported bugs. Importantly, this list is not sorted randomly. It is ordered by priority, with the most urgent item at the top. The term also has a second meaning: in a company’s financial figures, backlog refers to the sum of orders that have already been signed but not yet fulfilled.

What an ordered task list reveals about a company

Every team has more ideas than time. The backlog makes this surplus visible instead of hiding it. Anyone reading the list from top to bottom immediately sees a team’s priorities. That’s exactly why the order is often fought over more fiercely than the tasks themselves.

A second reason is predictability. If a team knows how many tasks it can complete per month, it can roughly estimate from the length of the backlog how long something will take. That’s not an exact deadline, but it’s better than guessing. If the backlog keeps growing faster than it’s being worked through, that’s a warning sign. Either there aren’t enough people, or the demands are too high.

In the financial world, the order backlog is one of the most important metrics of all. An aircraft manufacturer with orders for the next eight years has a very secure future. A growing backlog is therefore seen as a good sign of revenue yet to come. But it can also mean that the company isn’t supplying its customers fast enough.

From wish list to the next work package

A single entry usually describes a goal from the users' perspective, not a technical instruction. One example: “Users should be able to reset their own password.” How this is implemented is decided by the team later. Each entry also gets an estimate of how much effort it requires. This estimate is rough, often just “small,” “medium,” “large.”

Usually one person is responsible for maintaining the list, often the Product Owner. This is the role that decides what benefits the product most. They reorder entries, remove outdated wishes, and rephrase unclear points. This regular tidying up is called Backlog Refinement.

Many teams work in fixed time periods of one to four weeks, known as sprints. At the start, they take the topmost entries from the large backlog and pull them into a smaller list for that period. This small list stays as untouched as possible during the sprint so the team can work with focus. The large backlog, on the other hand, may change at any time.

Backlogs in developer tools and in quarterly figures

Practically every project tool has a backlog built in, such as Jira, Trello, Asana, or GitHub. Anyone who opens a software project there often sees the open items as “issues.” This list is also publicly viewable for open-source projects. There, one can look up which bugs are known and what is currently being worked on.

In quarterly reports of publicly traded companies, the word appears in its financial sense. Defense, construction, and machinery companies usually state their order backlog in billions of euros. Providers of AI data centers also report how many years' worth of their capacity has already been sold. Analysts compare this figure with revenue to see how long the order coverage will last.

A common misconception is to mistake the backlog for a schedule. It states what is to be done, and in what order – not on which date. It should also not be confused with technical debt, i.e., the legacy issues in program code. Such legacy issues can indeed end up as entries in the backlog, but they are something different from the list itself.