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The Difference Between SLA, SLO, and SLI Service Quality Metrics

SLA vs SLO vs SLI, what’s the difference anyway? Workplace success relies on clear expectations to help leaders and employees thrive together. As such, the partnership between customer and provider requires the same clarity to maintain service satisfaction. This is why Service Level Agreements (SLAs), Service Level Objectives (SLOs), and Service Level Indicators (SLIs) exist in the first place.

Together, they help both parties agree on what the other should expect and deliver when it comes to uptime, performance, disasters, and other service categories that are important to them.

An SLA is the overall agreement. SLOs are the goals outlined in that agreement. SLIs are the actual measured results of the service that are compared to the SLO to determine if the agreement was followed.

Here we’ll dive into each one in more depth and determine how you can use these to build a better relationship with your clients and deliver something they are happy with.

SLA: Service Level Agreement

To fully understand what SLAs are, we will go over the definitions along with examples and components that make up an SLA.

What Are SLAs?

Short for Service Level Agreement, an SLA is essentially a written contract between the client and service provider that details what services will be provided and at what standards.

This agreement lists the expectations of both parties and holds them accountable for different parts of the deal. For example, an SLA will have performance requirements on a specific API that the service provider will have to deliver on, but it could also involve that contingency that the client only sends a certain number of requests to that API a day.

How to Measure SLAs?

SLAs for web or application performance can measure KPIs such as uptime, downtime, response time and errors. There are many types of metrics you can track, but you don’t want to include too many. It is important to determine which metrics matter the most, and prioritize them. Learn more about how to measure and SLA, and the key KPIs to track.

Why Are SLAs Valuable?

SLAs are great for managing the expectations of both parties so they can determine if both parties are upholding their end of the agreement. This is to ensure that the relationship is beneficial for them and where they can improve if it isn’t.

Components of an SLA

Although every SLA is different, you can see the following general categories inside an SLA:

• The information of both parties
• Description of services provided
• List of technologies
• Sources of support
• Hours of operation
• Support levels for network, software, and/or hardware
• Services not offered in the agreement
• Service metric agreements
• Uptime
• Performance
• Availability
• Penalties and bonuses
• If metrics are not met, what are the penalties? If the metrics are exceeded, are there bonuses?
• Security measurements
• What measurements are being taken to prevent security risks? If security breaches happen, what will be the processes?
• Disaster recovery and risk management
• Reporting methods and frequency of reporting
• Termination policy

SLO: Service Level Objective

SLO is an acronym for Service Level Objective, which is a sub-component of an SLA.

What Are SLOs?

An SLA is the overall agreement between your business and the client, while SLOs are the specific, individual goals you made with them—the measurement that you want to hit.

An example of an SLO is that a business agrees to have one of its APIs up 99.9% of the time with an average response rate of 100 ms.

The key to a good SLO is its ability to be measured easily so that it is clear whether the team has hit the goal. The SLO should identify key metrics, not a full list of every metric that could be tracked. Due to an SLA’s bi-directional nature, it should also account for client-side delays and errors as well.

Why Are SLOs Valuable?

SLAs tend to be more abstract and generalized, but SLOs are concrete and measurable, which DevOps and technical teams tend to prefer. Because an SLO defines a clear, measurable goal, devs can track metrics and will know if they have hit the mark on those objectives or not.

Components of an SLO

SLO components vary based on what they are measuring, but overall, they consist of the following:

• What will be tracked.
• Uptime, performance of specific endpoints or pages.
• Measurements.
• How will the key metrics be tracked? Time could be in milliseconds. Uptime can be tracked by percentages over a specified time.

SLI: Service Level Indicator

SLIs are important to know if you want to compare SLOs with your current metric results.

What Are SLIs?

Service Level Indicators measure how well you comply with the SLO. So if your SLA says your response times need to be at 100 ms, then your SLO is measuring that response time in ms with an objective of 100 ms. And then let’s say your actual average response time was 96 ms. That actual time is your SLI.

Why Are SLIs Valuable?

Without SLIs, you won’t have real measurements to compare against your SLO to determine if you’ve met the expectations of the SLA.

Components of an SLI

SLIs are similar to SLOs in that they also use the same key metrics and measurements so that they can be compared to the SLOs.

Getting an Effective SLA, SLO, SLI

The SLA is crafted around the customer’s wants and needs. The best way to get an effective SLA (which can be abstract and generalized) is to make sure it’s as simple as possible, with simple metrics, deliverables, and a clear understanding from both sides of what is expected of them.

Focusing an SLA around the customer’s wants and needs will increase your chances of client satisfaction and a better partnership.

SLOs should be clear and only track the most important metrics. If you track too many unnecessary metrics, it could slow down dev processes or cause more confusion for the customer.

It is also worth building an error budget as things go wrong on both sides all the time. Remember Murphy’s law that anything that can go wrong will go wrong, and add that cushion into the agreement.

Combining SLAs, SLOs, and SLIs

Once SLAs and SLOs are finalized, the final step is to communicate your SLIs and paint the entire picture for the client. There are two ways you can do this.

Public SLA Pages

Public SLA pages allow you to display your checks for your clients so they can have a view of the SLO and SLI metrics. Uptime.com gives you access to this page along with the following components:

• Display your Uptime.com checks at a public or private URL
• Grant others access to reports without sharing your account access
• Display Summary Metrics: global uptime, outages, and total downtime

This sample page shows a simplified SLA webpage that can easily communicate the current SLA status.

These pages are great for:

• Displaying targeted checks and metrics for user visibility to manage expectations
• Facilitating a direct communication channel between your team and service users for informed conversations about your service performance
• Exposing reliable third-party SLA reporting to your customers

SLA Reports

SLA Reports provide a more in-depth way to show your SLA metrics and results. Uptime.com allows you to configure your report based on different needs so you can present your SLA data to stakeholders in the best way. Learn more about SLA reporting tips and best practices here.

Individual checks are shown in the SLA report: uptime, outages, downtime, and average response time within configurable time ranges that are your SLO metrics.

Customers can easily compare SLO targets with the actual SLI values in the reports because they are set as columns side by side.

Now that you know that difference between an SLA vs SLO vs SLI, you know that they are essentially for managing clear expectations, and SLA pages and reports help communicate those expectations to the stakeholders in an easy, visual way.

For more information on what else you can see in the SLA report, visit Uptime.com’s report page.

Looking to set up your own SLA report? Get started with Uptime.com’s 14-day free trial today. No credit card is required to start tracking your metrics and create your report in minutes!

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