Having recently migrated a mid-sized microservices architecture from a self-hosted Prometheus stack to a managed service (AWS Managed Service for Prometheus), I have concrete data to share. The decision often hinges on a simple trade-off: operational overhead versus predictable cost. However, the reality is more nuanced, involving cardinality management, long-term storage, and the true cost of engineer time.
Let's break down the key dimensions:
* **Infrastructure & Operational Burden:** Self-hosted requires managing the entire lifecycle: VM/container provisioning, storage (often with Thanos or Cortex for scalability), high availability, backups, and upgrades. A managed service abstracts this. My team spent approximately 8-10 engineering hours per month on maintenance and scaling alerts for our self-hosted cluster.
* **Cost Structure:** Self-hosted costs are primarily infrastructure (compute, storage, networking) and engineer time. Managed services charge per metric sample ingested, per query, and for storage duration. Our analysis showed that for our volume (~2.5 million active series), the managed service cost was 15-20% higher in pure dollars, but it freed up those 8-10 hours for feature development.
* **Performance & Scalability:** Self-hosted performance is limited by your own hardware and configuration tuning. Managed services typically offer near-instant horizontal scaling. We observed a 40% reduction in 99th percentile query latency during high-cardinality investigative queries after migrating, as the platform handled the query distribution seamlessly.
* **Advanced Features:** Managed services often bundle robust long-term storage, built-in high availability, and tighter integration with their ecosystem's alerting (e.g., Amazon SNS, GCP Cloud Monitoring). Replicating this self-hosted is possible but adds significant complexity.
Here is a simplified cost comparison for our scenario over a 12-month period:
```yaml
Self-Hosted (Annual):
- 3 x c5.2xlarge instances: ~$2,800
- 5 TB EBS gp3 storage: ~$500
- Estimated engineering maintenance (10 hrs/mo): ~$24,000
- Total (with eng. time): ~$27,300
Managed Service (Annual):
- Ingestion (2.5M series): ~$9,500
- Query costs: ~$1,200
- Storage (13 months retention): ~$3,600
- Total: ~$14,300
```
*Note: Engineering cost is estimated at a blended rate. Your actual "free" engineering time may be valued differently.*
The verdict is not universal. For small, stable deployments with dedicated platform engineers, self-hosted Prometheus remains a compelling, low-dollar-cost option. For dynamic, growing environments where developer velocity is paramount, the managed service provides a superior total cost of ownership by converting capital expenditure (engineering time) into a predictable operational expense.
So, is it worth it? The data suggests yes, if your series count is high and your team's opportunity cost is significant. The break-even point seems to be around 1 million active series and/or a lack of in-house SRE expertise dedicated to monitoring.
benchmark or bust
benchmark or bust