Errata

The last sentence of the first paragraph of the "File-Based Storage" section reads "File-based storage is commonly used for storing structured data, such as documents, images, videos, and audio files." I believe this should be "unstructured data", as those file formats are generally considered to be unstructured.

Note from the Author or Editor:
remove the "structured" word from the line. Update the line to "... used for storing data, such as documents ....."

The book says 'A sender sends a UDP segment to a destination on a specific port.'

In the context of UDP, the correct term is datagram, not "segment."

Note from the Author or Editor:
Makes sense. We should update the term "segment" with "datagram". This should be done for entire "User Datagram Protocol" section
1. holds the minimum data for segment delivery -> datagram delivery
2. order of segments -> order of datagrams
3. A sender sends a UDP segment -> A sender sends a UDP datagram

In the example ...

type FoodItem {
id: String!
name: String!
rating: Float
isVeg: Boolean!
}
query {
Restaurant (id: “lsoa34444lsoa”) {
name
foodItems {
name
description
}
}
}

Here - FoodItem does not have a 'description' attribute.
In GraphQL, queries are strongly typed and validated against the schema before they are executed. If you request a field (like description) that isn't defined in the type (FoodItem), the query is invalid and will return an error like:
The query will fail with 'Cannot query field "description" on type "FoodItem".'

Either the FoodItem type should have 'description' attribute, or 'description' should be removed from the query.

Note from the Author or Editor:
query to be updated (replace description with rating) -

query {
Restaurant (id: "lsoa34444lsoa") {
name
foodItems {
name
rating
}
}
}

Problem statement: “A route table in AWS defines network traffic both in and out of a subnet.”

---

What’s Wrong with This Clause?

1. Route Tables Only Affect Outbound Traffic

- *AWS Route Tables* control how *outbound traffic* (traffic leaving resources in the subnet) is routed.
- When a resource in the subnet initiates a connection, the route table determines where the packet goes (e.g., to the internet gateway, NAT gateway, or another subnet).
- *Inbound traffic* (traffic coming from outside to the subnet) is *not controlled by the subnet’s route table*. Instead, it is controlled by:
- The route table of the destination subnet (for traffic originating within the VPC)
- The presence of a public IP and a route to the IGW (for internet traffic)
- *Security groups* and *network ACLs* (NACLs) for packet filtering

2. Inbound Traffic Is Determined by Other Factors

- For traffic from the internet, the *return path* is established only if:
- The resource has a public IP/Elastic IP
- The subnet has a route to the IGW
- Security group and NACL rules allow it
- The route table does *not* determine whether unsolicited inbound internet traffic can reach a resource.

3. Example

- If you have a web server in a public subnet with a public IP:
- Outbound: When the server sends traffic to the internet, the route table directs it to the IGW.
- Inbound: When a user tries to access your web server, AWS’s infrastructure routes the packet to your public IP, and the IGW delivers it to your subnet. The route table is not consulted for this inbound path; instead, security groups/NACLs are checked.

---
Suggested:
Route tables in AWS only control outbound traffic from a subnet, not inbound traffic.
(Inbound access is managed by security groups, NACLs, and whether the resource has a public IP and a route to the IGW.)

Note from the Author or Editor:
Remove this sentence entirely from the paragraph for clarity --

"Route tables direct network traffic in and out of a subnet, but they don’t apply any security filters on this traffic. "

Problem sentence:
"Network load balancer (NLB)
Operates at the network layer (L4) for TCP, UDP, and TLS protocols"

L4 is the Transport Layer. 'network layer (L4)' should be replaced with 'transport layer (L4)'

Note from the Author or Editor:
Update the statement -

Operates at the fourth layer of OSI model supporting TCP, UDP, TCP_UDP, TLS, QUIC, and TCP_QUIC protocols.

'AWS recommends the S3 storage class over reduced redundancy as it is more cost-effective.' I sense that something is missing here. Which S3 storage class does AWS recommend over reduced redundancy?
The word 'Standard' is missing.

The sentence should perhaps read -
'AWS recommends the S3 Standard storage class over reduced redundancy as it is more cost-effective.'

Note from the Author or Editor:
Yes, this should be updated to include 'Standard' keyword for clarity.