Three Backups, One Point of Failure: What a 4 a.m. Outage Taught Me Before an SAP Cutover

Last week I was asked to support a weekend cutover for an SAP brownfield migration. If you've done one, you know the mindset. You plan for what breaks. Every critical step has a fallback, every fallback has an owner, and you hunt down single points of failure before they hunt you down.

Then, on Thursday 15 October, at 4 a.m., my own home infrastructure taught me the same lesson. Free of charge, as a hands-on training session, on my terrace, in the dark.

The Setup – Everything Fine on Paper

Since February I've lived in a new residential complex in District IX (Ferencváros), right in the middle of Budapest. On paper I'm well covered:

• Telekom fibre with an optical router – my primary connection.
• A USB mobile-internet stick with a Telekom SIM – my backup.
• Both Telekom and One are present in the complex, so in theory there is a choice.

In practice, there is almost no Telekom mobile signal inside the building. My phone only works through Wi-Fi calling. My USB backup stick only works where there is mobile signal – which is to say, not in my apartment.

The Night It All Lined Up

On the Terrace with Vanda

So there I was, on my terrace, in the dark, at 7 °C, with a single bar of 5G, calling customer service. First I reached Vanda, Telekom's virtual assistant. Vanda asked for my "MT" customer number – and told me to open the app to find it. But the app doesn't work without internet, and I had none: not at home, not on mobile. Vanda couldn't authenticate me. I kept trying.

About two or three minutes later, an SMS arrived. Telekom was sorry that my conversation with Vanda, the virtual assistant, had been unsuccessful.

The failure worked perfectly. Even the apology was automated.

Between 4 and 5 a.m., after waiting, I managed to talk to Telekom three times. The answer was the same each time: they were performing maintenance that was taking longer than expected.

On paper the process worked: there was a contact, a response and an apology. In reality I was exactly where I started – no internet, no phone, on a cold terrace. These are the moments that cost you not only time, but nerves – and probably a few more gray hairs.

Maintenance – Without Notice

I received no advance notice of the maintenance. If it was planned, why weren't customers told beforehand? And if it took longer than expected – while taking down both fibre and mobile internet – then something probably didn't go to plan. Did it get stuck? Did it fail? Was there a rollback plan?

I don't know. But maintenance that, before dawn and without notice, takes down fixed-line and mobile data at the same time, while the customer can't even authenticate, isn't maintenance. It's an incident.

Not Out of the Blue

The missing coverage isn't news. I filed a formal complaint with Telekom back in March, the emails went on for months, and in the end the property management received an offer: paid coverage for the underground garage only. For the flats, Telekom still recommends Wi-Fi calling – exactly what disappeared together with the internet that morning.

I've written up the full correspondence, how long each step took, and my questions in a separate case study.

What This Has to Do with SAP Cutovers

Everything in that story is a pattern I see in migration projects.

1. Backups that share a dependency with the primary aren't backups

My fibre, my phone and my USB stick all depended on one provider. On a cutover, that's the fallback system on the same network segment, or the rollback that needs the very system that just failed.

2. Automation without a human escape route amplifies failure

A bot that, in the middle of an internet outage, asks you to authenticate through an app that needs the internet, followed by an automated apology, closes the loop on paper and leaves the customer exactly where they started. Hypercare channels need the same thinking: when the automated path fails, who picks up?

3. Known issues become normal

When 240+ households have lived with the same gap since moving in, it stops being an incident and becomes the environment. The garage answer – a fix for a fee – treats a structural gap as an upsell. Projects do this too, with workarounds that quietly become permanent.

4. Test your fallback under real failure conditions

My backup looked fine until the moment I needed it. Dress rehearsals exist for exactly this reason – not to prove the plan works, but to find out where it doesn't.

5. Maintenance is a change too – with notice and a rollback plan

Unannounced maintenance that overruns and takes down both fixed-line and mobile data along the way – in an SAP project, that would be a change with no communication and no working rollback plan. On a cutover, the maintenance window is known in advance, we know who notifies whom, what the go/no-go criteria are, and when we roll back if things don't go to plan.

Practical Tips If You're in a Similar Situation

• Make your backup truly independent. Different provider, different technology, different physical path. If mobile internet is your backup, choose a provider that demonstrably has signal inside your home – measure it on the spot, in several rooms.
• Before moving in, test mobile coverage inside the apartment, not just on the street or on a coverage map.
• Test your backup with a real failure. Unplug the optical router and see what still works: internet, phone, and the ability to report the fault.
• Plan your fault-reporting path in advance. If your phone relies on Wi-Fi calling, reporting the outage won't work exactly when you need it.
• Keep your customer number offline. If customer service asks for the customer number from the app, it won't be reachable during an internet outage. Write it down, or save it on your phone offline.
• Shared problem – shared action. When hundreds of households in one complex are affected by the same gap, report it together and in a documented way. That is what moved things forward in my Digi case as well.

Related Case Studies

• Telekom Mobile Coverage at Cordia Woodland – Zero Signal in the Garage
• What a Modern Apartment Building's Internet and Wi-Fi Should Look Like
• High Availability in Home Office – redundant internet for remote work
• Digi Kft/One Complete Internet Outage – Haller Street 23-25