> For the complete documentation index, see [llms.txt](https://huang-jason.gitbook.io/ruby-rails-syntax/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://huang-jason.gitbook.io/ruby-rails-syntax/enterpriserails.md).

# Enterprise Rails - big picture

## Chap 1 - Big picture

Some criteria make a site feel like it's enterprise.

* service level agreement(SLA) for end-to-end load times.
* 99.99%(four nines) uptime.
* Scales linearly.
* fault tolerant.

DBA = database administrator Release engineer = manage release / create deployment plans / roll out IT = information technology engineer: store backup / logfiles

### 1. Growing

```
# 1. basic
DB ----- Rails app

# 2. basic + failover & redundency
DB ----- Rails app ----- Load balancer
 |
Warnm standby DB

# 3. A front-end web backed by services
DB --- service A --- Load balancer ---
 |                                   |
Warnm standby DB                     |--- Front-end --- Load balancer
                                     |
DB --- service B --- Load balancer ---
 |
Warnm standby DB
```