Composite SLOs and Setting the Right Reliability Targets

Setting Composite SLOs is Hard. This Calculator Makes it Easy.

Most reliability tracking focuses on one service at a time. That works fine until you realize that most user experiences rely on multiple services working together. Microservices, databases, APIs, and other components must function in sync for a seamless experience. On top of that, end-to-end user journeys often rely on services that have no synchronous APIs at all. If one piece fails, the whole experience can suffer. 

Composite SLOs are a game changer for end-to-end reliability and customer experience management. They let you group multiple SLOs into a single composite error budget, making measuring the full user experience across interconnected and dependent services more straightforward. 

Nobl9 is the only company currently offering this kind of comprehensive SLO management.

However, this raises another complication. With so many SLOs bundled into one error budget, how do you know what the overall reliability goal should be? How much should each service contribute? How do you avoid setting unrealistic targets or putting too much weight on something that barely matters?

These are tough questions; until now, answering them has been a bit of a guessing game. But it doesn’t have to be.

We built a calculator that makes the whole process easy
👉 Try it out here

Why Composite SLOs Are So Tricky

If you’re setting an SLO for a single service, the process is fairly straightforward. But when you have multiple services working together, there are a couple of schools of thought and some critical questions you must ask yourself.

Which ones matter most? 

Not every failure is equally painful. More weight should be placed on the SLOs or services known to impact the bottom line. 

How much weight should each one carry? 

A slow page load is annoying, but a failed payment is a deal-breaker. Focus weight on the deal-breakers to make the most efficient composite SLO possible.

What the final SLO target should be? 

It’s not just about meeting or missing a target. The key is setting the threshold at the point where user experience starts to degrade or where sustained high burn rates indicate deeper service issues. When combining multiple SLOs into one, this number becomes even more critical and hard to set. Set it too low, and you might overlook real problems. If you set it too high, you could create unnecessary alerts that don’t reflect actual user impact.

How the Calculator Helps

Our Composite SLO Calculator takes the guesswork out of the process. It’s built using the methodology from our documentation on choosing targets (guide here) and choosing weights (guide here).

Here’s how it works:

1. List the key SLOs that make up your user experience. Identify the individual services that contribute to the overall experience, such as database performance, API latency, or payment processing success rates.
2. Assign weightings based on business impact. Some services are more critical than others. Use the calculator to distribute weight based on how failures in each area affect overall reliability.
3. Set a realistic reliability target. The calculator factors in your weightings and individual SLOs to suggest a composite target that reflects when reliability truly starts to break down.

Instead of spending hours figuring this out manually, you get clear, data-backed guidance in minutes.

Start Using the Calculator Today

Defining a composite SLO that truly reflects your system's behavior can be challenging. This tool simplifies the process and gives you a structured, data-driven way to set the right targets.

 Get the Composite SLO Calculator Now

Nobl9 provides the best user experience for defining and managing composite SLOs. If you want to take control of your reliability at the experience level, you need Nobl9. Try it out and see the difference for yourself.

Prefer to get a detailed look at how composite SLOs are set up within the Reliability Center? One of our experts is happy to show you!