Migrate a SIEM without a cutover weekend

Why the weekend cutover fails

The conventional migration picks a date, repoints every source, and hopes Monday looks like Friday. It usually does not. Parsers behave differently. Field names shift. Rules that relied on a vendor-specific function fail quietly. The team then spends a quarter rebuilding what it had, while paying for both platforms anyway.

The alternative is to run both platforms on identical data for as long as it takes to prove parity, then stop paying attention to the old one. This only works if routing lives upstream of both platforms, in a layer you control.

Stage one: put the pipeline in front

Point every source at CyberAIX Pipeline once. Configure the incumbent SIEM as the sole destination. Nothing changes for analysts. What has changed is that adding or removing a destination is now an edit to a routing table rather than a visit to two hundred source configurations.

Stage two: mirror

Add the new platform as a second destination receiving the same stream. Do not migrate any rules yet. Instead, run a daily comparison of event counts per source across both platforms. Sources that parse differently on the new platform will show up here first, while there is still time to fix them quietly.

Stage three: triage the rulebook

Export the incumbent's detection content and sort it into three piles.

• Protected. Tied to a compliance requirement or a known active threat. Migrate first, test hardest.
• Live. Fired at least once in the last quarter. Migrate second.
• Dormant. Everything else. Review, and expect to retire most of it.

Because normalization now happens in the pipeline, most rule translations are syntax rather than schema work.

Stage four: validate under real load

Analysts keep working in the incumbent. Every alert that fires there should have a twin in the new platform. Track every mismatch to its root cause. When the mismatch count has been zero for a period you have agreed in advance, you have your cutover criterion.

An adversary emulation exercise run against both platforms at the same time is the fastest way to surface coverage differences you did not think to test for.

Stage five: flip on a criterion, not a date

Move analyst workflows to the new platform. Leave the incumbent receiving data but unattended for a final quiet period. Then remove it from the routing table. Its historical data goes to inexpensive storage where CyberAIX Federated Search can still reach it.

Mistakes worth avoiding

• Migrating dormant rules because they were there.
• Skipping the daily parity check and discovering ingestion gaps from an incident.
• Letting the old contract's end date decide when you are ready.