Metrics Platform: Junior → Architect Evolution
The mandated interactive flow. Step through each rung, ask what breaks FIRST, weigh the options, and defend the chosen architecture. This is how architectural thinking is learned — not by reading a fixed design, but by tracing how it evolves under growth pressure.
Scale Evolution Timeline
Step through 6 architectural rungs, from 10K RPS to 1B RPS. At each rung, ask: what will break FIRST? Why? What options exist? Which one do we pick — and what are we accepting?
This is the reasoning cycle that separates a Junior developer ("here's an architecture") from an Architect ("here's why this architecture, why now, and what breaks next").
10K time-series/sec — Prometheus + Grafana
1. Current architecture
Where we are before growth pressure
Single Prometheus server (5m retention) + Grafana dashboards.
2. Growth trigger
What changed — the traffic/data force
Early product. 50 services × 100 metrics = 5K time-series. Prometheus scrapes every 15s.
3. Bottleneck — what breaks FIRST?
The component that saturates as growth arrives
None yet
Prometheus handles millions of samples per second on single node.
CPU 15%, RAM 8 GB, retention 15d local
4. Options — what could we do?
Alternatives an architect must consider before picking
- + Standard tool
- + Free
- − Local storage limit
- − SPOF
5. Chosen
The specific decision we're making
Do nothing — Prometheus + Grafana is right at MVP
6. Trade-offs
What we're explicitly accepting to move forward
- Accept local storage 15d limit
- Accept SPOF
7. New architecture
The system after this decision — headroom for the next 5-10x
1 Prometheus + Grafana. Total: $100/mo.
8. Next bottleneck — what will break at the NEXT rung?
This is the seed of the next rung
At ~100K time-series/sec + need for long-term storage + high-cardinality (user_id label = millions of series), Prometheus single-node ceiling hit.
What comes next in your Junior → Architect journey
You've traced 6 rungs of Metrics Platform evolution. Now try the same reasoning cycle on a system you don't know yet — pick from the Systems catalog and answer the same questions: current arch → growth trigger → bottleneck → options → chosen → trade-offs → new arch → next bottleneck. That is architecture.