# Part 9 — Deployment & Infrastructure

> How the systems you've designed actually get built, shipped, run, and paid for. The gap between "it
> works on the whiteboard" and "it runs reliably in production."

**Time for this part:** Week 10 on the Standard track. Deployment and operations come up in senior
design interviews as "how would you deploy/scale/run this?" — and cost is the single most
under-used seniority signal in the whole loop.

The unifying idea: **operability is a design property.** Containers, orchestration, CI/CD, deployment
strategies, and IaC all exist to make deploying and running software safe, repeatable, and reversible —
and to make "how is this configured?" a question with an answer.

---

## Chapters

### Packaging and running

| # | Chapter | Time | The problem it solves |
| --- | --- | --- | --- |
| 1 | [VMs, Containers, and Docker](./01-containers.md) | 18 min | Shipping the environment with the code |
| 2 | [Kubernetes for System Designers](./02-kubernetes.md) | 20 min | Orchestrating hundreds of containers — and when not to |
| 7 | [Cloud Provider Primitives](./07-cloud-primitives.md) | 16 min | The same building blocks under different names |

### Shipping safely

| # | Chapter | Time | The problem it solves |
| --- | --- | --- | --- |
| 3 | [CI/CD Pipelines](./03-ci-cd.md) | 16 min | Frequent, small deploys are safer than rare, large ones |
| 4 | [Deployment Strategies](./04-deployment-strategies.md) | 16 min | Zero downtime and limited blast radius |
| 5 | [Feature Flags & Progressive Delivery](./05-feature-flags.md) | 16 min | Decoupling deploy from release |
| 6 | [Infrastructure as Code](./06-infrastructure-as-code.md) | 14 min | Version-controlled, reproducible infrastructure |

### Running at scale

| # | Chapter | Time | The problem it solves |
| --- | --- | --- | --- |
| 8 | [Multi-Region & Disaster Recovery](./08-multi-region-and-dr.md) | 22 min | Surviving a region failure; serving the globe |
| 9 | [Capacity Planning & Autoscaling](./09-capacity-and-autoscaling.md) | 16 min | How much you need, and why autoscaling isn't magic |
| 10 | [Cost Optimization](./10-cost-optimization.md) | 16 min | The bill is a design constraint |

---

## The things to remember

1. **Containers are isolated processes** (namespaces + cgroups), not lightweight VMs — and they ship
   the environment with the code, killing "works on my machine."
2. **Kubernetes is declarative desired state with a reconciliation loop** — that's what makes it
   self-healing. And most teams adopt it before they need it.
3. **Frequent small deploys are safer**, not riskier — build the artifact once, promote it, and make
   rollback fast.
4. **Canary limits blast radius; blue-green gives instant rollback; feature flags decouple deploy from
   release.** Every zero-downtime strategy runs old and new versions together, so they must be
   compatible.
5. **Multi-AZ is cheap resilience; multi-region is a big, deliberate step.** Active-active's hard part
   is writes — shard by region to avoid conflicts. And test your DR, or it doesn't work.
6. **Autoscaling lags and can't handle spikes or cascades**; the database doesn't scale with the app
   tier. Keep headroom.
7. **Cost is a design concern.** Egress is the #1 surprise. Bringing up cost unprompted is a strong
   seniority signal.

---

## Before moving on

You should be able to answer these without notes:

- [ ] Explain the difference between a VM and a container, and why containers are just processes.
- [ ] Explain Kubernetes' declarative/reconciliation model and when *not* to use it.
- [ ] Explain why frequent small deploys are safer, and why to build the artifact once.
- [ ] Compare canary, blue-green, and rolling on blast radius vs rollback speed.
- [ ] Explain how feature flags decouple deploy from release, and flag debt.
- [ ] Explain RTO/RPO and the active-active write-conflict problem.
- [ ] Explain why autoscaling can't handle sudden spikes, and the app-tier/database mismatch.
- [ ] Name the top cost drivers, especially egress, and the main pricing-model levers.

---

**Next:** [Part 10 — Performance & Scaling Playbooks](../10-performance/) — the concrete techniques for
finding and fixing bottlenecks, and the story of scaling from one user to a billion.