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Make some minor wording/formatting changes (#120)

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@ -556,7 +556,7 @@ Services such as [CloudFlare](https://www.cloudflare.com/dns/) and [Route 53](ht
### Disadvantage(s): DNS ### Disadvantage(s): DNS
* Accessing a DNS server introduces a slight delay, although mitigated by caching described above. * Accessing a DNS server introduces a slight delay, although mitigated by caching described above.
* DNS server management could be complex, although they are generally managed by [governments, ISPs, and large companies](http://superuser.com/questions/472695/who-controls-the-dns-servers/472729). * DNS server management could be complex and is generally managed by [governments, ISPs, and large companies](http://superuser.com/questions/472695/who-controls-the-dns-servers/472729).
* DNS services have recently come under [DDoS attack](http://dyn.com/blog/dyn-analysis-summary-of-friday-october-21-attack/), preventing users from accessing websites such as Twitter without knowing Twitter's IP address(es). * DNS services have recently come under [DDoS attack](http://dyn.com/blog/dyn-analysis-summary-of-friday-october-21-attack/), preventing users from accessing websites such as Twitter without knowing Twitter's IP address(es).
### Source(s) and further reading ### Source(s) and further reading
@ -727,9 +727,7 @@ Additional benefits include:
<i><a href=http://lethain.com/introduction-to-architecting-systems-for-scale/#platform_layer>Source: Intro to architecting systems for scale</a></i> <i><a href=http://lethain.com/introduction-to-architecting-systems-for-scale/#platform_layer>Source: Intro to architecting systems for scale</a></i>
</p> </p>
Separating out the web layer from the application layer (also known as platform layer) allows you to scale and configure both layers independently. Adding a new API results in adding application servers without necessarily adding additional web servers. Separating out the web layer from the application layer (also known as platform layer) allows you to scale and configure both layers independently. Adding a new API results in adding application servers without necessarily adding additional web servers. The **single responsibility principle** advocates for small and autonomous services that work together. Small teams with small services can plan more aggressively for rapid growth.
The **single responsibility principle** advocates for small and autonomous services that work together. Small teams with small services can plan more aggressively for rapid growth.
Workers in the application layer also help enable [asynchronism](#asynchronism). Workers in the application layer also help enable [asynchronism](#asynchronism).
@ -1259,8 +1257,8 @@ Refresh-ahead can result in reduced latency vs read-through if the cache can acc
### Disadvantage(s): cache ### Disadvantage(s): cache
* Need to maintain consistency between caches and the source of truth such as the database through [cache invalidation](https://en.wikipedia.org/wiki/Cache_algorithms). * Need to maintain consistency between caches and the source of truth such as the database through [cache invalidation](https://en.wikipedia.org/wiki/Cache_algorithms).
* Need to make application changes such as adding Redis or memcached.
* Cache invalidation is a difficult problem, there is additional complexity associated with when to update the cache. * Cache invalidation is a difficult problem, there is additional complexity associated with when to update the cache.
* Need to make application changes such as adding Redis or memcached.
### Source(s) and further reading ### Source(s) and further reading
@ -1742,9 +1740,9 @@ Handy metrics based on numbers above:
#### Source(s) and further reading #### Source(s) and further reading
* [kilimchoi/engineering-blogs](https://github.com/kilimchoi/engineering-blogs) Looking to add a blog? To avoid duplicating work, consider adding your company blog to the following repo:
The list of blogs here will be kept relatively small and [kilimchoi/engineering-blogs](https://github.com/kilimchoi/engineering-blogs) will contain the larger list to avoid duplicating work. Do consider adding your company blog to the engineering-blogs repo instead. * [kilimchoi/engineering-blogs](https://github.com/kilimchoi/engineering-blogs)
## Under development ## Under development