SLO Anti-Patterns: Real-World Lessons
Tags: sre, slo, reliability, devops
Published: 2023-02-21 17:06:52

Service Level Objectives (SLOs) are a crucial aspect of modern software development and operations practices. SLOs are measurable targets that define the expected performance and availability of a software service. They are typically defined in terms of metrics such as uptime, response time, and error rates, and are used to guide engineering efforts and communicate service expectations to customers. SLOs can help ensure that engineering teams are aligned with business goals and customer needs, and can provide a framework for continuous improvement and optimization. By setting realistic and relevant SLOs, organizations can improve service reliability, reduce downtime, and enhance customer satisfaction.

Service Level Objectives (SLOs) are a critical part of any Service Level Agreement (SLA) between a service provider and its customers. However, there are some common anti-patterns that can cause SLOs to become ineffective or even harmful to a service's reliability. 

Here are some examples of SLO anti-patterns:

**- Overcommitting:** Setting SLOs that are too aggressive or ambitious can lead to missed targets and a lack of trust from customers. It's important to set realistic and achievable SLOs that can be met consistently.

**- Undercommitting:** Setting SLOs that are too lenient or easy to achieve can result in a lack of motivation for the team to continuously improve the service's reliability.

**- Focusing only on availability:** While availability is a critical component of SLOs, it's important to consider other performance metrics as well, such as latency, throughput, and error rates.

**- Ignoring customer needs:** SLOs should be based on the needs and expectations of the customers using the service. Failing to consider customer feedback and requirements can lead to SLOs that do not align with their needs.

**- Lack of transparency:** SLOs should be transparent and easily understood by customers, as well as the team responsible for meeting them. Failing to provide clear communication can lead to misunderstandings and a lack of trust.

Overall, it's important to approach SLOs with a balanced and customer-centric mindset, and to regularly review and adjust them based on feedback and performance data.

Now, let's say that a company provides an e-commerce service that allows customers to purchase goods online. The company has an SLA that promises 99.9% availability and a response time of no more than 500 milliseconds for all requests.

**- Overcommitting:** The company's engineering team sets a very aggressive SLO of 99.99% availability and a response time of 100 milliseconds. While this may sound impressive, it's unrealistic given the service's current infrastructure and the team's ability to manage it. As a result, the team consistently fails to meet the SLO, which erodes customer trust and damages the company's reputation.

**- Undercommitting:** On the other hand, the engineering team could set a very easy-to-achieve SLO, such as 95% availability and a response time of 1 second. While this may be achievable, it doesn't provide much motivation for the team to work towards improving the service's reliability. Additionally, customers may be dissatisfied with the lackluster performance of the service.

**- Focusing only on availability:** The company's engineering team becomes obsessed with meeting the availability SLO at the expense of other performance metrics. They focus solely on ensuring that the service is up and running, but don't pay attention to issues such as high latency or slow response times. As a result, customers may experience a slow and frustrating experience even if the service is technically available.

**- Ignoring customer needs:** The engineering team sets SLOs based solely on their own technical goals, without taking into account customer feedback or requirements. For example, the SLOs may be set to prioritize system uptime over order fulfillment speed, even if customers are more concerned about getting their orders quickly.

**- Lack of transparency:** The company doesn't communicate its SLOs effectively to customers or provide sufficient information about how the service is performing. As a result, customers may be left in the dark about what to expect, and the company may not be held accountable for any lapses in performance.

Here are ten things to consider when coming up with SLOs:

1. Align SLOs with business objectives and customer needs.
2. Use clear and measurable metrics to define SLO targets.
3. Ensure SLOs are realistic and achievable.
4. Consider the service's expected workload and usage patterns.
5. Account for service dependencies and third-party integrations.
6. Define separate SLOs for different service components as needed.
7. Consider setting different SLOs for different user segments.
8. Continuously monitor and adjust SLOs as needed to meet changing conditions.
9. Communicate SLOs to relevant stakeholders, both internally and externally.
10. Use SLOs to guide decision-making and resource allocation for service improvements.

Remember that SLOs should be tailored to your specific service and the needs of your users, so it's important to take the time to define SLOs that are meaningful and useful for your particular context.