Update README.md

fixing typos

README.md

@@ -685,7 +685,7 @@ S3
 	-	[S3QL](https://github.com/s3ql/s3ql) ([discussion](https://news.ycombinator.com/item?id=10150684)) is a Python implementation that offers data de-duplication, snap-shotting, and encryption, but only one client at a time.
 	-	[ObjectiveFS](https://objectivefs.com/) ([discussion](https://news.ycombinator.com/item?id=10117506)) is a commercial solution that supports filesystem features and concurrent clients.
 -	If you are primarily using a VPC, consider setting up a [VPC Endpoint](http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpc-endpoints.html) for S3 in order to allow your VPC-hosted resources to easily access it without the need for extra network configuration or hops.
--	**Cross-region replication:** S3 has [a feature](https://docs.aws.amazon.com/AmazonS3/latest/dev/crr.html) for replicating a bucket between one region and a another. Note that S3 is already highly replicated within one region, so usually this isn’t necessary for durability, but it could be useful for compliance (geographically distributed data storage), lower latency, or as a strategy to reduce region-to-region bandwidth costs by mirroring heavily used data in a second region.
+-	**Cross-region replication:** S3 has [a feature](https://docs.aws.amazon.com/AmazonS3/latest/dev/crr.html) for replicating a bucket between one region and another. Note that S3 is already highly replicated within one region, so usually this isn’t necessary for durability, but it could be useful for compliance (geographically distributed data storage), lower latency, or as a strategy to reduce region-to-region bandwidth costs by mirroring heavily used data in a second region.
 -	**IPv4 vs IPv6:** For a long time S3 only supported IPv4 at the default endpoint `https://BUCKET.s3.amazonaws.com`. However, [as of Aug 11, 2016](https://aws.amazon.com/blogs/aws/now-available-ipv6-support-for-amazon-s3/) it now supports both IPv4 & IPv6! To use both, you have to [enable dualstack](http://docs.aws.amazon.com/AmazonS3/latest/dev/dual-stack-endpoints.html) either in your preferred API client or by directly using this url scheme `https://BUCKET.s3.dualstack.REGION.amazonaws.com`.
 -	**S3 event notifications:** S3 can be configured to send an [SNS notification](https://aws.amazon.com/blogs/aws/introducing-the-amazon-simple-notification-service/), [SQS message](http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/Welcome.html), or [AWS Lambda function](http://docs.aws.amazon.com/lambda/latest/dg/welcome.html) on [bucket events](http://docs.aws.amazon.com/AmazonS3/latest/dev/NotificationHowTo.html).
 
@@ -698,7 +698,7 @@ S3
 -	🔸Eventual data consistency, as discussed above, can be surprising sometimes. If S3 suffers from internal replication issues, an object may be visible from a subset of the machines, depending on which S3 endpoint they hit. Those usually resolve within seconds; however, we’ve seen isolated cases when the issue lingered for 20-30 hours.
 -	🔸**MD5s and multi-part uploads:** In S3, the [ETag header in S3](http://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html) is a hash on the object. And in many cases, it is the MD5 hash. However, this [is not the case in general](http://stackoverflow.com/questions/12186993/what-is-the-algorithm-to-compute-the-amazon-s3-etag-for-a-file-larger-than-5gb) when you use multi-part uploads. One workaround is to compute MD5s yourself and put them in a custom header (such as is done by [s4cmd](https://github.com/bloomreach/s4cmd)).
 -	🔸**US Standard region:** Previously, the us-east-1 region (also known as the US Standard region) was replicated across coasts, which led to greater variability of latency. Effective Jun 19, 2015 this is [no longer the case](https://forums.aws.amazon.com/ann.jspa?annID=3112). All Amazon S3 regions now support read-after-write consistency. Amazon S3 also renamed the US Standard region to the US East (N. Virginia) region to be consistent with AWS regional naming conventions.
--	❗When configuring ACLs on who can access the bucket and contents, a predefined group exists called **[Authenticated Users](http://docs.aws.amazon.com/AmazonS3/latest/dev/acl-overview.html)**. This group is often used, incorrectly, to restrict S3 resource access to authenticated users of the owning account. If granted, the AuthenticatedUsers group will allow S3 resource access to **all authenticated users, across all AWS accounts**. A typical use case of this ACL is used in conjuction with the [requester pays](http://docs.aws.amazon.com/AmazonS3/latest/dev/RequesterPaysBuckets.html) functionality of S3.
+-	❗When configuring ACLs on who can access the bucket and contents, a predefined group exists called **[Authenticated Users](http://docs.aws.amazon.com/AmazonS3/latest/dev/acl-overview.html)**. This group is often used, incorrectly, to restrict S3 resource access to authenticated users of the owning account. If granted, the AuthenticatedUsers group will allow S3 resource access to **all authenticated users, across all AWS accounts**. A typical use case of this ACL is used in conjunction with the [requester pays](http://docs.aws.amazon.com/AmazonS3/latest/dev/RequesterPaysBuckets.html) functionality of S3.
 
 ### Storage Durability, Availability, and Price
 
@@ -729,7 +729,7 @@ EC2
 
 -	Running EC2 is akin to running a set of physical servers, as long as you don’t do automatic scaling or tooled cluster setup. If you just run a set of static instances, migrating to another VPS or dedicated server provider should not be too hard.
 -	🚪**Alternatives to EC2:** The direct alternatives are Google Cloud, Microsoft Azure, Rackspace, DigitalOcean and other VPS providers, some of which offer similar API for setting up and removing instances. (See the comparisons [above](#when-to-use-aws).)
--	**Should you use Amazon Linux?** AWS encourages use of their own [Amazon Linux](https://aws.amazon.com/amazon-linux-ami/), which is evolved from from [Red Hat Enterprise Linux (RHEL)](https://en.wikipedia.org/wiki/Red_Hat_Enterprise_Linux) and [CentOS](https://en.wikipedia.org/wiki/CentOS). It’s used by many, but [others are skeptical](https://www.exratione.com/2014/08/do-not-use-amazon-linux/). Whatever you do, think this decision through carefully. It’s true Amazon Linux is heavily tested and better supported in the unlikely event you have deeper issues with OS and virtualization on EC2. But in general, many companies do just fine using a standard, non-Amazon Linux distribution, such as Ubuntu or CentOS. Using a standard Linux distribution means you have an exactly replicable environment should you use another hosting provider instead of (or in addition to) AWS. It’s also helpful if you wish to test deployments on local developer machines running the same standard Linux distribution (a practice that’s getting more common with Docker, too, and not currently possible with Amazon Linux).
+-	**Should you use Amazon Linux?** AWS encourages use of their own [Amazon Linux](https://aws.amazon.com/amazon-linux-ami/), which is evolved from [Red Hat Enterprise Linux (RHEL)](https://en.wikipedia.org/wiki/Red_Hat_Enterprise_Linux) and [CentOS](https://en.wikipedia.org/wiki/CentOS). It’s used by many, but [others are skeptical](https://www.exratione.com/2014/08/do-not-use-amazon-linux/). Whatever you do, think this decision through carefully. It’s true Amazon Linux is heavily tested and better supported in the unlikely event you have deeper issues with OS and virtualization on EC2. But in general, many companies do just fine using a standard, non-Amazon Linux distribution, such as Ubuntu or CentOS. Using a standard Linux distribution means you have an exactly replicable environment should you use another hosting provider instead of (or in addition to) AWS. It’s also helpful if you wish to test deployments on local developer machines running the same standard Linux distribution (a practice that’s getting more common with Docker, too, and not currently possible with Amazon Linux).
 -	**EC2 costs:** See the [section on this](#ec2-cost-management).
 
 ### EC2 Tips
@@ -1159,7 +1159,7 @@ Lambda
 -	🔸Lambda is a new technology. As of mid 2016, only a few companies are using it for large-scale production applications.
 -	🔸Managing lots of Lambda functions is a workflow challenge, and tooling to manage Lambda deployments is still immature.
 -	🔸AWS’ official workflow around managing function [versioning and aliases](https://docs.aws.amazon.com/lambda/latest/dg/versioning-aliases.html) is painful.
--	🔸Currently, [Lambda does not natively provide for environment variables](https://forums.aws.amazon.com/thread.jspa?messageID=686261), which are a [common way](https://12factor.net/config) of storing configuration, so your must rely on additional mechanisms to achieve this (such as the [Serverless framework](https://serverless.com/framework/docs/guide/environment-variable-handling/#environment-variables-in-serverless) or [apex](http://apex.run/#environment-variables)).
+-	🔸Currently, [Lambda does not natively provide for environment variables](https://forums.aws.amazon.com/thread.jspa?messageID=686261), which are a [common way](https://12factor.net/config) of storing configuration, so you must rely on additional mechanisms to achieve this (such as the [Serverless framework](https://serverless.com/framework/docs/guide/environment-variable-handling/#environment-variables-in-serverless) or [apex](http://apex.run/#environment-variables)).
 -	❗📜 Currently [as of October, 2016](https://github.com/open-guides/og-aws/pull/199/files/c99bddb4ee2437587f1e188d47be2bb1da01f81d#r83529126) Lambda functions can sometimes stop working for 2-3 minutes for failure recovery purposes according to a support ticket answer from Lambda development team. They are working to prevent this in the future.
 
 🚧 [*Please help expand this incomplete section.*](CONTRIBUTING.md)
@@ -1267,7 +1267,7 @@ VPCs, Network Security, and Security Groups
 -	**Port hygiene:** A good habit is to pick unique ports within an unusual range for each different kind of production service. For example, your web frontend might use 3010, your backend services 3020 and 3021, and your Postgres instances the usual 5432. Then make sure you have fine-grained security groups for each set of servers. This makes you disciplined about listing out your services, but also is more error-proof. For example, should you accidentally have an extra Apache server running on the default port 80 on a backend server, it will not be exposed.
 -	**Migrating from Classic**: For migrating from older EC2-Classic deployments to modern EC2-VPC setup, [this article](http://blog.kiip.me/engineering/ec2-to-vpc-executing-a-zero-downtime-migration/) may be of help.
 -	For basic AWS use, one default VPC may be sufficient. But as you scale up, you should consider mapping out network topology more thoroughly. A good overview of best practices is [here](http://blog.flux7.com/blogs/aws/vpc-best-configuration-practices).
--	Consider controlling access to your private AWS resources through a [VPN](http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpn-connections.html).
+-	Consider controlling access to you private AWS resources through a [VPN](http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/vpn-connections.html).
 	-	You get better visibility into and control of connection and connection attempts.
 	-	You expose a smaller surface area for attack compared to exposing separate (potentially authenticated) services over the public internet.
 		-	e.g. A bug in the YAML parser used by the Ruby on Rails admin site is much less serious when the admin site is only visible to the private network and accessed through VPN.
@@ -1425,9 +1425,9 @@ Kinesis Streams
 
 -	📒 [Homepage](https://aws.amazon.com/kinesis/streams/) ∙ [Developer guide](https://docs.aws.amazon.com/streams/latest/dev/introduction.html) ∙ [FAQ](https://aws.amazon.com/kinesis/streams/faqs/) ∙ [Pricing](https://aws.amazon.com/kinesis/streams/pricing/)
 -	**Kinesis Streams** (which used to be only called Kinesis, before Kinesis Firehose and Kinesis Analytics were launched) is a service that allows you to ingest high-throughput data streams for immediate or delayed processing by other AWS services.
-- Kinesis Streams’ subcomponents are called [**shards**](https://docs.aws.amazon.com/streams/latest/dev/key-concepts.html). Each shard provides 1MB/s of write capacity and 2MB/s of read capacity at a maximum of 5 reads per second. A stream can have its shards programatically increased or decreased based on a variety of metrics.
+- Kinesis Streams’ subcomponents are called [**shards**](https://docs.aws.amazon.com/streams/latest/dev/key-concepts.html). Each shard provides 1MB/s of write capacity and 2MB/s of read capacity at a maximum of 5 reads per second. A stream can have its shards programmatically increased or decreased based on a variety of metrics.
 - All records entered into a Kinesis Stream are assigned a unique sequence number as they are captured. The records in a Stream are ordered by this number, so any time-ordering is preserved.
-- [This page](http://docs.aws.amazon.com/streams/latest/dev/key-concepts.html) summarises key terms and concepts for Kinesis Streams.
+- [This page](http://docs.aws.amazon.com/streams/latest/dev/key-concepts.html) summarizes key terms and concepts for Kinesis Streams.
 
 ### Kinesis Streams Alternatives and Lock-in
 
@@ -1444,7 +1444,7 @@ Kinesis Streams
 
 ### Kinesis Streams Gotchas and Limitations
 
-- 🔸⏱  Kinesis Streams’ shards each only permit [5 reads per second](http://docs.aws.amazon.com/streams/latest/dev/service-sizes-and-limits.html). If you are evenly distrubuting data across many shards, your read limit for the Stream will remain at 5 reads per second on aggregate, as each consuming application will need to check every single shard for new records. This puts a hard limit on the number of different consuming applications possible per Stream for a given maximum read latency.
+- 🔸⏱  Kinesis Streams’ shards each only permit [5 reads per second](http://docs.aws.amazon.com/streams/latest/dev/service-sizes-and-limits.html). If you are evenly distributing data across many shards, your read limit for the Stream will remain at 5 reads per second on aggregate, as each consuming application will need to check every single shard for new records. This puts a hard limit on the number of different consuming applications possible per Stream for a given maximum read latency.
    - For example, if you have 5 consuming applications reading data from one Stream with any number of shards, they cannot read with a latency of less than one second, as each of the 5 consumers will need to poll *each shard* every second, reaching the cap of 5 reads per second per shard.
 	- [This blog post](https://brandur.org/kinesis-in-production) further discusses the performance and limitations of Kinesis in production.
 -	💸 **Kinesis Streams are not included in the free tier.** Make sure if you do any experimentation with it on a personal account, you shut down the stream or it may run up unexpected costs (~$11 per shard-month.)