Alright, I'm probably going to get some heat for this, but after implementing and managing both at my last two companies, I've come to a conclusion.
Splunk ES is a fantastic, comprehensive framework. For a large, mature security team with dedicated Splunk admins and analysts, it's the way to go. But for the other 80% of companies? The overhead is immense. You're paying a hefty premium for a lot of pre-built content (correlation searches, data models, dashboards) that you then have to *heavily* tune anyway. The complexity often leads to:
* Slower time-to-value during implementation.
* A "black box" feeling where you're not entirely sure why a notable event fired.
* Significant resource drain for maintenance and upgrades.
Instead, I've seen more success with a core Splunk Enterprise instance, meticulously tuned for performance, paired with a custom-built app targeting the company's *actual* top risks. You own the logic, the data flow, and the alerts completely.
For example, our "cloud access monitoring" app was just a few hundred lines of SPL and some Python scripts feeding a simple dashboard. It was faster to build, easier for new team members to understand, and cost a fraction of ES.
```sql
index=aws_cloudtrail eventName=ConsoleLogin
| stats values(userIdentity.userName) as users by eventTime, userIdentity.sessionContext.sessionIssuer.userName
| search users>3
| eval risk_score=if(match(userIdentity.sessionContext.sessionIssuer.userName, "assumed-role"), 10, 5)
```
The key is having a clear data model and knowing your own environment. ES tries to be everything for everyone, which is its strength but also its biggest weakness for leaner teams.
Am I crazy? Has anyone else gone the custom route after feeling the ES bloat? Especially curious about scaling this approach past the initial use cases.
Data is the new oil - but it's usually crude.
You're spot on about the tuning overhead. Even with ES, we ended up disabling about half the pre-packaged correlation searches out of the gate because they didn't fit our data or produced too much noise.
That custom app approach you mentioned is golden for focus. We did something similar for Salesforce login monitoring. Built a lightweight app that just tracked admin logins, bulk exports, and session hijacking patterns. The team actually understood the SPL behind the alerts, which made tuning them a breeze.
The only caveat I'd add is watch out for alert fatigue in a homegrown system. It's easy to get clever and build too many alerts without the built-in triage workflow ES gives you. You have to be disciplined about building a simple review process from the start.
The 80% figure is painfully accurate, but I think even that lets ES off the hook. The real issue isn't just the tuning overhead, it's the institutional paralysis it creates.
You get sold a "turnkey" SOC, but what you actually buy is a dependency. When your one Splunk admin who understands ES's quirks leaves, you're left with a brittle, expensive monument that nobody fully understands how to modify. That "black box" feeling becomes a permanent state of affairs. At least with a custom app, the bus factor is higher because the logic is something you built, not something you inherited and are afraid to touch.
The premium you pay is for the illusion of completeness, which is the most expensive feature of all.