Why AWS Spot Instances Become Impossible to Get in December

Understand why Spot capacity drops dramatically in December, how this impacts your deployments, and the strategies you can use to avoid interruptions.

I. Why AWS Spot Instances Become Impossible to Get in December  

EC2 Spot Instances are a fantastic way to save 50–70% on your AWS compute costs.
They use the unused capacity of AWS data centers… but in December, this unused capacity almost completely disappears.

Result:

• Auto Scaling Groups fail to launch new instances
• deployments get stuck
• “insufficient capacity” everywhere
• Spot interruptions become much more frequent

If you’ve experienced this, rest assured: it’s not your fault, and not a configuration issue.
It’s a seasonal phenomenon, and it happens every single year.

In this article, we break down why Spot Instances become nearly impossible to obtain in December, which AWS services are impacted most, and—most importantly—how to anticipate and survive this annual event. With a hint of humor… and a sprinkle of holiday spirit.

II. Why December Breaks Spot Instances  

1. Massive Demand Before the Holidays  

December is the month of:

• e-commerce overload (Black Friday through Christmas),
• massive advertising campaigns,
• mobile games exploding in traffic,
• financial year-end batch workloads,
• seasonal spikes in web traffic.

As a result, major players (Amazon Retail, advertisers, fintech, gaming, SaaS) consume huge amounts of EC2 capacity.

AWS prioritizes On-Demand customers.
And Spot? Well… Spot is whatever empty seat remains on the plane.

2. AWS Internal Maintenance & Operations  

The end of the year usually means a release freeze for many companies… but AWS uses this period for:

• holiday staffing constraints,
• hardware rotation and replacement,
• preparing new instance generations,
• internal capacity rebalancing.

When AWS temporarily removes servers from circulation, Spot instances are the first to disappear.

3. Some Regions Are Particularly Fragile  

The newer or smaller a region is, the weaker its Spot capacity tends to be. Examples:

• eu-west-3 (Paris),
• eu-south-1 (Milan),
• eu-south-2 (Spain)

Even highly popular AZs in us-east-1 often run at peak load in December.

Typical December observations:

• Standard CPU families (c5, c6i, etc.) → unavailable
• Memory-optimized families (r5, r6i) → saturated
• GPU → essentially impossible

If your workload depends on a single instance family, December is… frustrating.

III. Typical December Symptoms  

This is what you’ll usually see in your logs:

• insufficientCapacity: The capacity is not available. Normal in December
• Spot interruptions increase sharply. They jump from 1–5%… to 20–40% on some days.
• Auto Scaling Groups stuck in Pending for minutes… then hours. A sign that your cluster is competing with the entire planet.
• max price exceeded: AWS adjusts Spot prices based on demand. In December, it’s almost normal to see temporary price spikes.”

If these issues appear only in November/December.That’s expected.

IV. What We Observe in the Real World  

Year after year, the pattern is remarkably consistent:

V. How to Survive December if You Use Spot Instances  

1. Set Up an On-Demand Fallback  

This is the most effective strategy:

• use a mixed Auto Scaling Group: Spot + On-Demand
• guarantee at least 20–30% baseline On-Demand capacity
• let AWS fill the rest with Spot if available

Simple, effective, and avoids surprise outages.

2. Allow Multiple Instance Types  

Even without advanced solutions, an ASG can accept multiple instance families:

Examples:

• c5.large, c5a.large, c6i.large
• m5.large, m5a.large, m6i.large
• t3.medium, t4g.medium

You can diversify instance sizes and AZs as well.

The more options you give AWS, the higher the chances of finding available capacity.

3. “Bursting windows” (when workload is predictable)  

For batch workloads:

• Run jobs early in the morning.That’s when best Spot availability
• Avoid 18:00–23:00.It’s peak saturation
• Avoid Fridays and Mondays

4. Monitor Spot Placement Scores  

AWS exposes a Spot placement score via the API and the console.
This score tells you which regions and AZs currently have better Spot capacity.

Very useful for multi-region architectures or temporary migrations.

5. Avoid Critical Infrastructure Changes in December  

December is unstable.
If possible, avoid:

• instance type migrations,
• major infrastructure changes,
• creation of new critical ASGs.

6. Accept That December Is a “Red Month” for Spot  

It’s not a myth:
year after year, December is the hardest month for Spot capacity.

Normal conditions usually return between January 5th and 10th.

Conclusion  

December is a magical month… except for Spot Instances.
Demand surges, AWS capacity tightens, and Spot availability drops dramatically.

With minimal preparation:

• On-Demand fallback,
• Multi-type ASGs,
• Anticipation of peak loads,

… you can get through the holiday season without unpleasant surprises.

Take the opportunity to slow down, review your cloud costs, and prepare for a more optimized year.

🔗 Useful Links  

• Official Amazon EC2 Spot Documentation
• AWS Spot Best Practices
• Spot Placement Score Explained