Diary of an Engineering Manager - Task Breakdown and Estimation

The Art of Task Breakdown and Estimation

If you ask any software engineer or engineering manager about one of the top skills they need, most will say it’s the ability to break down a feature or large project into tasks and estimate the time and effort required. If you ask them what part of their job they dread the most, they’ll often give the exact same answer. We like to think that building a software project is like building a house, where we have a blueprint and know exactly what to do. But the truth is, building a house is often simpler than building a software project, at least when it comes to estimation and planning. Software projects vary in size, complexity, and in the number of variables that can affect the outcome. For example, building a new service from scratch can be simpler in some cases than updating an existing one, while in other cases it can be the opposite. A project that relies on existing code might be simpler than one that requires a complete rewrite, but this can vary widely as well.

Because of this, it’s hard to transfer estimation skills directly from one project to another. Here, I’ll discuss some approaches I’ve used to break a big project into smaller deliverables and to estimate the time required to complete them.

The Importance of Task Breakdown

The way you break down a project into tasks is as important as the actual code itself. A good breakdown can make the difference between a project that’s delivered on time and one that isn’t. It helps you identify dependencies, required resources, and the overall path to completion. The first steps of any software project typically involve understanding the requirements, clarifying constraints, and creating a detailed, approved design.

Once the design is set, it’s time to break the project down. I’ve seen many developers and managers approach this from the bottom up, grouping related tasks together. But while this might seem logical, it often makes it harder to show incremental progress or accurately estimate the total time.

Instead, I recommend a top-down approach that starts by defining higher-level “capabilities,” which can then be broken down into smaller tasks. In Agile methodologies, these capabilities closely resemble “epics” or “stories.” If a capability is relatively small and can be completed in a single iteration, it's similar to a story (a concise piece of user-facing functionality that can be delivered and demonstrated at the end of a sprint). If the capability is larger and spans multiple iterations, it’s more like an epic and will need to be decomposed into multiple stories. Personally, I prefer to call this capability, because we are not always building user-facing products.

For example, if you’re building a new shopping website, you might define the following capabilities:

• A user can register and log in to the website
• A user can view the product catalog
• A user can add products to the shopping cart
• A user can check out and complete a purchase
• A user can view order history

Each capability is a self-contained feature that can be delivered independently.
One capability might require changing or working with multiple parts of the codebase, as opposed to the bottom-up approach.
You then break each capability into tasks. For instance, “A user can register and login” might break down into:

• Create a new user account
• Authenticate the user
• Redirect the user to the login page
• Handle the login process
• Redirect the user to the home page

Defining capabilities isn’t an exact science. It requires a good understanding of the project and some practice. Some projects make it easier to define capabilities, while others require more thought. But understanding the principles behind this approach will guide you toward a better breakdown.

The Importance of Task Estimation

Once you have a solid breakdown into capabilities and tasks, it’s time to estimate how long each task will take. This is often the most dreaded part of any project. However, with a good process, it becomes less painful. Agile methodologies such as Scrum or Kanban provide frameworks for estimation, but the specifics may vary depending on the team or project. Here, I’ll discuss a process I’ve found useful.

First, accept that no one can estimate time with 100% accuracy. There will always be unknowns that affect the outcome. Still, you can arrive at reasonable estimates by following a structured process. It’s also best if people who are familiar with the codebase or have done similar work in the past provide the estimates. If you’re not familiar with the codebase, reach out to someone who is before estimating.

One approach is to come up with two estimates for each task: the optimistic "best case" estimate and the pessimistic "worst case" estimate. The actual estimate can be the average of the two. Another approach is to provide a single estimate and then add a buffer (say 20%) to account for surprises.

In my experience, we often forget to include testing and pull request review time in our estimates. Testing usually takes longer than writing the code itself. Also, pushing and reviewing the PR can be significant. Make sure these times are included. And remember that finishing the code doesn’t mean the project is done. Complex projects often need integration with other services, thorough testing, and compliance with engineering standards before reaching production. Sometimes there’s even a security review or other formal processes that add time.

Deployment Time

Congratulations, you’ve completed the coding, testing, and all required processes. You’re ready to deploy. In many mature companies, code doesn’t reach production instantly. Instead, it passes through multiple environments and “bake times” to catch any issues before hitting production. This adds more time, and you need to account for it when promising delivery dates.

The good news is that if you’ve broken down your project into capabilities, some can reach production earlier than the final release date. This flexibility can help ensure the overall project is delivered on time.

Conclusion

There is no silver bullet for project breakdown and estimation, but best practices do help. I highly recommend breaking the project down into capabilities, as this approach gives you more flexibility and higher confidence as the project evolves. Over time, you’ll refine these skills and become more comfortable making reliable estimates that guide your projects to successful conclusions.