Performance monitoring and logs.
With the same sentry SDKs that report your errors, Fehlo measures requests and page loads and collects your logs. All on one server in Nuremberg, in the same tool as your errors.
Performance
The sentry SDKs measure requests, page loads and background jobs as transactions. For each transaction, such as GET /api/orders, Fehlo shows:
- throughput, median (p50), p95 and failure rate, searchable and sortable,
- the trend over days and the split by span: database, HTTP calls, templates,
- N+1 queries, the same database query run in a loop.
To switch it on, set a sample rate in the SDK, for example one request in five:
traces_sample_rate=0.2,tracesSampleRate: 0.2,What Fehlo doesn't have: a waterfall view of single traces, Web Vitals, profiling, mobile app starts. Fehlo stores transactions aggregated, not one by one.
What transactions and logs cost
Transactions and log lines each have their own allowance and don't count as events, which cover errors only. A transaction counts once, however many spans it contains.
| Plan | Transactions a month | Log lines a month | Events a month |
|---|---|---|---|
| Free, €0 | 100,000 | 250,000 | 5,000 |
| Solo, €9 a month | 1,000,000 | 2,500,000 | 100,000 |
| Team, €29 a month | 5,000,000 | 10,000,000 | 500,000 |
| Agency, €79 a month | 20,000,000 | 40,000,000 | 2,000,000 |
When the transactions run out, Fehlo pauses only performance data until the billing month ends. Errors, logs and uptime keep coming in, and nothing is charged extra. Prices net, plus VAT.
For comparison: Sentry includes 5 million spans in every plan, the free one too.1 At ten spans per transaction that is 500,000 transactions, more than Fehlo's Free plan. From Team up, Fehlo includes more: 5 million transactions rather than 5 million spans.
Logs
Logs from the sentry SDKs land in Fehlo next to your errors:
- search in text and attributes, filters by level, service and host,
- a histogram over time and a live view that shows new lines as they arrive,
- a trace filter to see every line of one request.
Log lines count against their own allowance; the numbers per plan are in the table above. When they run out, Fehlo pauses only logs until the billing month ends; errors, performance data and uptime keep coming in. Logs are kept for 30 days, like events.
For comparison: Sentry includes 5 GB of logs in every plan.1 A log line is usually 0.2 to 1 KB, so 5 GB is roughly 5 to 25 million lines.
Where the data lives
Transactions and logs often hold more personal data than errors: URLs with query parameters, database queries, log lines with customer numbers. At Fehlo they sit on the same server in Nuremberg as everything else. What the SDKs send by default and how to limit it is on GDPR-compliant error tracking.
Sources
- Sentry pricing page, sentry.io/pricing, retrieved 24 October 2026.
Sentry is a trademark of Functional Software, Inc. Fehlo is not affiliated with Sentry.
Questions
Do I need a different SDK for performance?
No. The same sentry SDK that reports errors measures transactions once you set tracesSampleRate (JavaScript) or traces_sample_rate (Python).
What happens when the transactions run out?
Fehlo stops accepting performance data until the billing month ends. Errors, logs and uptime keep running. There is no pay as you go and no extra charge for transactions.
What happens when the log lines run out?
Fehlo stops accepting logs until the billing month ends. Errors, performance data and uptime keep running. There is no pay as you go for logs either.
Does Fehlo show single traces?
No. Fehlo shows transactions aggregated with p50, p95, failure rate and span breakdown. There is no waterfall view per request.