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Multi-region serverless backend — reloaded
Accelerating Serverless Applications with Global Accelerator and Application Load Balancer
In 2018, I wrote a series of blog posts on building a multi-region, active-active, serverless architecture on AWS [1, 2, 3 and 4]. The solution was built using DynamoDB Global Tables, Lambda, the regional API Gateway feature, and Route 53 routing policies. It worked well as a resiliency pattern and as a disaster recovery (DR) strategy . But there was an issue.
Brace yourself: DNS isn’t perfect
DNS is one of the most important services on the Internet as it turns a user-friendly domain name like amazon.com into an IP address that computers use to identify each other and direct traffic to a network.
To do so, the DNS service uses a hierarchy of name servers distributed around the world that try to answer a simple question: “what is the IP for that particular domain name?” If a name server cannot answer the question, it may query another name server higher in the hierarchy. This process is called recursive query.
Now imagine if every time you typed a domain name on your browser or every time you used an app on your phone, the DNS service had to repeat the entire process from scratch and query all the name servers in the recursion chain. This would be slow, resource-intensive and prone to failure.
Caching to the rescue
Luckily, the designers of the DNS service thought about that and specified the use of a time-to-live (TTL) for every DNS record. Caching name servers use that TTL configuration to determine how long the result of a particular DNS query should be stored. DNS caching improves the efficiency of the DNS service as it reduces the DNS traffic across the Internet, but also serves as a resiliency technique because it prevents overloads of the authoritative name-servers, particularly the root name-servers which sit at the top of the hierarchy.
Because they can speed up resolution of the query, DNS caching servers increase…
