I thought uptime monitoring was solved. Then I started building one.
When an agency client says:
“The site feels slow.”
That’s usually the beginning of a very painful conversation.
Because by the time users notice:
- leads may already be dropping
- conversions may already be affected
- support tickets may already be coming in
- the client may already think nobody was watching
That’s the part of monitoring I underestimated when I started building Sentinel.
I thought uptime monitoring was mostly about detecting outages.
But agencies deal with a different problem:
sites that are technically “up,” while the experience is already degrading.
A site can still return 200 OK while:
- DNS resolution slows down
- TLS negotiation starts failing intermittently
- TTFB spikes in one region
- a CDN edge behaves differently geographically
- third-party scripts delay rendering
- content partially fails to load
From the outside, the system looks healthy.
But the client experience isn’t.
One thing that changed my perspective recently was breaking response timing into phases instead of treating performance as a single number.
I started separately tracking:
- DNS lookup time
- TCP connection time
- TLS handshake time
- time to first byte
That exposed patterns I never would’ve seen from “response time” alone.
Sometimes the earliest warning sign isn’t downtime.
It’s friction.
And for agencies managing dozens of client sites, catching that degradation before the client notices is where monitoring becomes genuinely valuable.
That's usually how it goes though - you don't really see the gaps until you're deep in the weeds building it yourself. What made you finally pull the trigger on it?
That’s the real wedge.
Most monitoring tools are still selling uptime to technical buyers.
Agencies are buying client trust.
That’s a very different product.
The useful signal here is not “did the site go down.”
It’s “did the client notice before we did.”
That is the actual failure event agencies pay to avoid.
Once you frame it that way, Sentinel stops looking like another uptime tool and starts looking more like client-facing risk infrastructure.
That positioning likely matters more than the feature list.
Also worth watching:
“Sentinel” is familiar enough to explain the category, but generic enough that it may cap how proprietary the product feels if this expands past agency monitoring.
Exirra.com would carry more weight if you push this further into trust / performance infrastructure.
Exactly.
“Did the client notice first?” is starting to feel like the metric that actually matters.
A lot of agencies already have uptime monitoring somewhere in their stack.
What they really care about is reducing the chances of painful client conversations.
That framing changed how I think about the product quite a bit.