I once worked with a small product team that rolled out a new feature late on a Friday. The deployment looked smooth, dashboards stayed green, and we packed up for the weekend.
By Saturday morning, customer messages surged. The app wasn’t loading, checkout screens froze, and people were stuck. The service was technically running, but no one could use it.
The issue took hours to fix, and the team learned a difficult lesson: Even a brief period of downtime can ripple through revenue and user trust.
If you’re in DevOps, SRE, or IT, you already know downtime is inevitable. But knowing what counts as downtime, what causes it, and how to reduce it is what turns an outage into a short-lived hiccup rather than an expensive failure.
Let’s break it down in simple terms.
Table of Contents
What is Downtime?
Downtime is any period when a system, application, or service is unavailable to users.
Users may not be able to load a page, complete a workflow, or access features.
Downtime can last a few seconds or several hours. The duration matters, but so does the impact. A 2-minute incident at midnight might not cause a lot of damage, but the same incident during a flash sale could cost millions and shake customer trust.
Example of Downtime
Imagine you open a shopping app. If the app won’t load at all, that’s downtime. And if the app loads but checkout fails or payment errors keep popping up, that’s downtime too, because you still couldn’t perform the actions you wanted to.
The same idea goes across services as well: If users can’t perform their intended action, like logging in, searching, placing an order, or paying, the system is “down” from their perspective, even if it appears to be running at your end.
What causes downtime
Downtime can happen for many reasons. Common causes include hardware failure, software incidents, overloaded systems, configuration errors, network issues, or data center outages.
Planned maintenance can also contribute, though it’s often excluded from SLA calculations.
How to calculate downtime
Downtime is the total time a service is unavailable within a given window.
Formula: Downtime = Total Time − Uptime
Let’s consider a week where the system goes down a few times for 3 days. 10 minutes down on Monday, 8 minutes on Wednesday, and 30 minutes on Friday. Hence, it makes up to a total of 48 minutes of downtime in that week. Even short, scattered outages add up and can impact user experience.
Some teams also track downtime by counting failed requests or periods where error rates exceed a threshold.
Two Types of Downtime
1. Planned downtime
This is scheduled ahead of time for work like maintenance, patching, upgrades, database changes, or migrations.
Teams plan it during low-traffic windows to reduce disruption. Because users are notified, it usually doesn’t violate SLAs.
Examples:
- Database version upgrades
- Security patching
- Hardware swaps
Planned downtime is often excluded from SLA calculations.
At Spike, we once scheduled a 30-minute maintenance window (planned downtime) to move from a self-hosted database to MongoDB Atlas. We announced it on our status page and brought alerts and the status page back within the first 5 minutes. We also emailed updates before and after, and kept support open for our users.
2. Unplanned downtime
This is sudden and unpredictable. It interrupts service without any warning and often causes the most disruption for users and on-call teams.
Common triggers:
- Hardware failures
- Software bugs
- Networking issues
- Misconfigurations
- Security breaches
Unplanned downtime is costly because it directly disrupts business operations, causing loss in revenue, missed transactions, SLA penalties, and a spike in support workload.
Engineering teams must drop ongoing work to investigate and remediate the issue, delaying feature development and escalating labor costs. The longer the outage lasts, the more these losses compound.
How To Reduce Downtime
Downtime will happen. The goal isn’t to reach zero outages. That’s unrealistic. Instead, the real win is reducing how often outages occur and how long they last. The focus shifts from elimination to resilience and rapid recovery.
Here are a few practical strategies that help teams cut downtime:
- Have backups for critical services to take over during failures
- Use load balancing to distribute traffic evenly and prevent overload
- Invest in incident response tools like Spike to get alerts for incidents before they spiral
- Maintain rollback strategies so teams can quickly revert to bad deployments
- Practice chaos testing to find weak spots before they break under real pressure
Conclusion
Downtime is any period when users can’t use your service. Planned downtime keeps systems healthy. Unplanned downtime hurts revenue, trust, and SLAs.
Reducing downtime isn’t just about cleaner dashboards; it protects revenue, user trust, and your brand’s long-term credibility. Even short outages can derail transactions or frustrate customers enough to leave for a competitor.
That’s why it pays to invest in resilience: build redundancy, monitor proactively, plan safe rollbacks, and pressure-test systems. The goal isn’t perfection, but faster recovery and fewer surprises.
When teams take downtime seriously and prepare intentionally, outages turn from chaos into manageable blips, and the business keeps moving forward.
FAQs
1. How much downtime is 99% uptime?
99% uptime equals about 7 hours and 18 minutes of downtime per month, or roughly 3.65 days per year.
2. What is downtime in production?
Production downtime occurs when a live system or service becomes unavailable to users, often caused by crashes, overloads, or deployment errors.
3. What is downtime in maintenance?
Maintenance downtime is planned unavailability for updates, patching, or infrastructure work. It’s typically scheduled and excluded from SLA calculations.
4. How much does downtime cost?
Costs vary widely by industry but can run into the millions of dollars per hour. For example:
- A 2014 Gartner report found that over one-third of enterprises lose $1-5 million for every hour of downtime.
- A 14-hour Facebook outage reportedly cost approximately US $6.3 million per hour, with a total hit of about US $90 million.
These figures show why minimizing downtime, planned or unplanned, isn’t just tech hygiene, but a business imperative.
5. How can downtime affect a company’s reputation?
Frequent or long outages erode customer trust, drive users to competitors, and can harm brand reliability—sometimes more than the financial loss itself.