Microservices Communication Tax
A growing engineering team decides to break their monolith into microservices. The promise: independent deployments, team autonomy, technology flexibility. The reality: every function call that was once in-process now crosses a network boundary. The communication tax compounds with every new service. P99 latency jumps 300-900% as requests hop across services. Simple database transactions become distributed sagas. Debugging a production issue that once meant reading a stack trace now requires distributed tracing across dozens of services. Amazon Prime Video famously moved back to a monolith and cut costs 90%. Segment did the same. The pattern repeats across the industry.
What people believe
“Microservices give teams independence and allow faster, safer deployments.”
| Metric | Before | After | Delta |
|---|---|---|---|
| P99 latency | 50ms | 200-500ms | +300-900% |
| Deployment units | 1 | 10-50 | +900-4900% |
| Infrastructure cost | $5K/mo | $15-25K/mo | +200-400% |
| Time to debug production issues | 1 hour | 4-8 hours | +300-700% |
Don't If
- •Your team is smaller than 30 engineers
- •Your monolith deploys in under 15 minutes
- •You don't have dedicated platform/infra engineers
- •Your scaling bottleneck is the database, not the application
If You Must
- 1.Start with 2-3 services at natural domain boundaries, not 50
- 2.Invest in observability before splitting — you'll need it
- 3.Define API contracts and versioning strategy upfront
- 4.Accept that you're trading code complexity for operational complexity
Alternatives
- Modular monolith — Domain boundaries without network boundaries
- Service-oriented monolith — Internal modules with clean interfaces, single deployment
- Selective extraction — Extract only the 1-2 services with genuine scaling needs
This analysis is wrong if:
- Teams under 30 engineers consistently report net productivity gains from microservices
- P99 latency does not increase meaningfully after decomposition
- Infrastructure costs remain flat or decrease after microservices adoption
- 1.Sam Newman — Building Microservices (2nd ed.)
Canonical reference acknowledging microservices tax
- 2.Martin Fowler — Microservice Prerequisites
Lists operational maturity requirements most teams lack
- 3.Segment Engineering Blog — Goodbye Microservices
Segment moved back to monolith after microservices complexity
- 4.Amazon Prime Video — Monolith Saves 90%
Prime Video moved from microservices to monolith, cut costs 90%
This is a mirror — it shows what's already true.
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