Post Mortem: Temp Mail Chaos on Black Friday – What We Wish We Had Known Earlier

Black Friday is notoriously the time of year when email inboxes worldwide go into overdrive. But for us at Müllmail, your trusted provider Temp Mail provider, this year’s Black Friday turned into a true trial by fire. What happened? Why did our system fail? And how did we overcome the chaos? This post mortem sheds light on the situation.

Black Friday and the Temp Mail Flood

We knew that Black Friday would be a heavy load for our system, but what happened this year exceeded all expectations. A prime example: One major retailer sent a whopping 12,000 emails within just five minutes – you could say we were too "Lidl" prepared. At that moment, our system simply wasn’t built to handle such a flood and promptly decided to go on strike.

A Frenzied Phase of Troubleshooting

The challenge was twofold: First, we had to identify the root cause – was it just the Black Friday rush, or were we under attack? Second, we worked around the clock to restore our service. This period was a stark reminder that even the smallest bottlenecks in infrastructure can snowball into massive disruptions.

Our Measures: Trial, Panic! & Error

To resolve the issues and future-proof ourselves, we took several measures. Here’s an overview:

1. Simplifying the Database Layout

As a first step, we streamlined our database layout to reduce CPU load. This brought only a minimal improvement but highlighted where the real bottlenecks were hiding.

2. Adjusting Mail Server Sizing

We allocated additional resources to our mail server – upgrading from 8 CPU cores to 16. It quickly became clear, though, that this wasn’t enough.

3. Adapting Email Processing

Another bottleneck was the processing and sanitization of incoming emails. Temporarily, we simplified these workflows, but when too many emails were delivered simultaneously, we hit our limits again. F#+!.

4. Server Upgrade

Finally, in a last-minute operation, we migrated to a much beefier server – from 32 cores to a 96-core powerhouse. Even so, this was only part of the solution.

The Solution: Rate Limiting, fool!

The real game-changer turned out to be the implementation of sensible rate limiting for incoming emails (gee, who would've thought?). This gave our system the necessary "breathing room" to process each email efficiently without an ever-growing backlog overloading the entire service. Since then, our system has been running smoothly again.

A Big Thank You to Our Users

We’d like to thank all Müllmail users for their patience and trust. We’ve learned a lot from this experience and will continue working hard to make our system even more robust and reliable. If you’re still experiencing delivery issues, feel free to reach out to us at kontakt@team.muellmail.com anytime.

What We Learned

Black Friday has shown us one thing: Even well-thought-out and previously "thought to be" battle-tested systems can quickly hit their limits when faced with unexpected loads. But thanks to the measures we implemented and the tireless efforts of our team, we overcame this challenge (knocking on wood as we say this). Our goal remains to be your go-to solution for Temp Mails in the future.