Where to start when you have no monitoring at all – and only an hour to set it up.
Direct answer: A SaaS startup should first monitor whatever directly touches paying customers: the main application, the login/authentication flow, and the core API. These are the failures that generate support tickets and churn within minutes. SSL, DNS and domain checks come next – they fail rarely, but silently, and can take the whole product offline.
Key takeaways
- Prioritise by customer impact, not by what’s easiest to monitor.
- Application, login and core API come first – they’re what customers notice immediately.
- SSL, DNS and domain checks are second-priority but non-negotiable – they cause full outages when neglected.
- You can have a working setup in under an hour; don’t let “the right tool” become an excuse to delay.
Why does monitoring order matter for a startup?
With limited engineering time, a startup can’t build a comprehensive monitoring stack on day one – and doesn’t need to. The right approach is to monitor the systems most likely to fail in a way customers notice first, then expand coverage as the product and team grow. Getting the order right means the checks you have in place actually catch the failures that matter, rather than covering edge cases while a core outage goes undetected.
What should be monitored first?
Three things, in this order:
- The main application. If customers can’t load the product, nothing else matters. This needs a Critical-priority HTTP check against the real application URL – not a health-check endpoint that always returns 200.
- The login/authentication flow. A broken login locks out every customer even if the rest of the app is technically “up.” It fails independently of general uptime and needs its own check.
- The core API. If your product is API-driven, or other services depend on your API, this is as customer-facing as the application itself and deserves the same priority.
Sentinel performs ongoing HTTP checks to confirm services are up, responding with the expected status code, and within expected response-time thresholds – which covers all three of these directly, as separate monitors with their own alert routing.
What should be monitored second?
Once the customer-facing critical path is covered, add the infrastructure that fails rarely but catastrophically:
- SSL certificate validity and expiry – see what happens when an SSL certificate expires.
- DNS record integrity, particularly around infrastructure changes.
- Domain registration status – see what happens when a domain expires.
These don’t need minute-by-minute checking, but they do need to be monitored – a lapsed domain or expired certificate takes down a healthy application just as completely as a server crash.
What can wait?
Marketing site performance, secondary/internal tooling, and scheduled jobs that aren’t customer-facing (internal reports, non-critical batch jobs) can be added once the core stack is in place. They matter, but they don’t block a first working monitoring setup.
Example: a minimum first-day setup
| Order | Monitor | Why first |
|---|---|---|
| 1 | Main application (HTTP) | Total outage, immediately visible to every customer |
| 2 | Login endpoint | Can fail independently of general uptime |
| 3 | Core API | Customer- or integration-facing failure |
| 4 | SSL certificate | Rare but total failure if it lapses |
| 5 | Domain registration | Rare but total failure if it lapses |
Original Sentinel evidence
Illustrative example using anonymised data.
Frequently asked questions
Do I need separate monitors for login and the general application?
Yes – they fail independently. A monitor on the homepage won’t catch a broken login page, and vice versa.
How long does it take to get this initial stack running?
Most users are monitoring their first service within 60 seconds of creating a Sentinel account; a five-monitor starter stack like the one above typically takes under an hour end to end.
Should scheduled jobs be part of the first-day setup?
Only if a job is directly customer-facing, such as billing. Non-critical internal jobs can be added once the core stack is running – see How to Monitor Cron Jobs and Scheduled Tasks for detail.
Get started
This is the starting point covered in full in the SaaS monitoring guide for small teams. Sentinel’s Team plan supports this stack and room to grow, from £30/month.