The Secret Life of AWS: The Traffic Director
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Translating names to numbers, smart routing policies, and why you should always use an Alias.
Part 8 of The Secret Life of AWS
Timothy was pacing back and forth in the West Wing, muttering under his breath.
"One-nine-two, dot, one-six-eight, dot, zero, dot, one. Five-four, dot, two-three, dot..."
Margaret looked up from her desk. "Are you reciting poetry, Timothy?"
"I am memorizing the IP addresses of our servers," Timothy said, rubbing his temples. "The web server is 54.23.1.5. The database is 10.0.2.9. It is impossible to remember them all. I keep dialing the wrong ones."
Margaret sighed and closed her ledger. "That is because you are trying to speak 'Computer.' Humans are not meant to speak Computer. We are meant to speak 'Human'."
She walked to the chalkboard and wiped it clean. "Today, we discuss Route 53. It is the Domain Name System (DNS) for AWS."
DNS (The Translation Layer)
Margaret drew two columns on the board: Name and Value.
"At its core," she explained, "DNS is a simple database. It maps a human-readable name to a machine-readable number."
She wrote an entry:www.timothys-library.com 54.23.1.5
"This is an A Record (Address Record). It connects a name directly to an IPv4 address. When a user types the name, Route 53 looks up the number and connects them. You never have to memorize the digits again."
"Simple enough," Timothy said. "I will create an A Record for everything."
"Not everything," Margaret corrected.
CNAME vs. Alias (The Pointers)
"Sometimes," Margaret continued, "you do not want to point to a specific number. You want to point to another name."
She wrote another entry:mobile.timothys-library.com www.timothys-library.com
"This is a CNAME (Canonical Name). It essentially says: 'I don't have an address, go ask that guy for his address.' It is useful when you want multiple names to lead to the same place."
"So it is a redirect?"
"Effectively. But there is a technical limitation. You cannot use a CNAME for the root of your domain (the Zone Apex). You cannot map timothys-library.com to another name using a CNAME."
Timothy looked confused. "But what if I need to point my root domain to a Load Balancer? AWS Load Balancers only have DNS names, not static IPs."
"Then you use the AWS special record: The Alias."
Margaret drew a star next to the entry. "An Alias is smart. It looks like a CNAME, but it behaves like an A Record. It allows you to map your root domain directly to AWS resources—like Load Balancers or S3 Buckets—completely for free."
Routing Policies (The Decision Maker)
Timothy nodded. "Okay. Names point to numbers. Is that all?"
"If it were a simple list, yes," Margaret said. "But Route 53 is programmable. It doesn't just look up numbers; it makes decisions based on Routing Policies."
She drew a diagram with a user in Japan and servers in London and Tokyo.
"Imagine a user connects from Japan. Which IP address should Route 53 give them?"
"The Tokyo one," Timothy said. "It is closer."
"Precisely. This is Latency-Based Routing. Route 53 detects that the user is in Japan, sees that the Tokyo server offers the lowest latency, and returns the Tokyo IP. A user in London requesting the same website would get the London IP."
Health Checks (Failover)
"That is clever," Timothy admitted. "But what if the Tokyo server crashes?"
Margaret drew a big X over the Tokyo server.
"If this were a static list," she said, "Route 53 would keep sending users to the dead server. They would get an error."
She drew a stethoscope icon on the board.
"Route 53 uses Health Checks. It constantly pings your servers to ask, 'Are you healthy?'"
"If Tokyo stops answering," she continued, "Route 53 instantly removes that IP from the rotation. The next time a Japanese user connects, Route 53 automatically gives them the London IP instead. We call this Failover Routing."
TTL (Time to Live)
"There is one last detail," Margaret added, writing TTL on the board.
"DNS responses are cached. When a user's computer looks up your website, it remembers the IP address for a certain amount of time. This is the Time To Live."
"If you set it to 24 hours," she warned, "and you change your server IP, users will still be trying to go to the old address for a full day. If you set it to 60 seconds, they will get the new address almost instantly, but Route 53 will charge you for more queries."
"It is a trade-off," Timothy noted.
"Engineering is always a trade-off," Margaret smiled.
The Lesson
Timothy looked at the board. It wasn't just a list of names. It was a dynamic logic map, routing traffic based on location and health.
"It is not just a network map," Timothy realized. "It is a traffic controller."
"It is the front door to your entire application," Margaret said. "If the DNS fails, it does not matter how perfect your servers are. No one can find them."
She handed him the eraser.
"Now, stop muttering numbers. Give your servers proper names. And Timothy?"
"Yes?"
"Use an Alias for the root domain. It is free."
Aaron Rose is a software engineer and technology writer at tech-reader.blog and the author of Think Like a Genius.
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