After this lesson, you will be able to: Wire AWS applications together with the integration services: SQS for queues, SNS for pub/sub, API Gateway in front of Lambda, and Route 53 for DNS.
Compute and storage are the nouns; the integration services are the verbs that connect them. SQS and SNS decouple components so a slow or failed part does not take the system down. API Gateway turns Lambda functions into real HTTP APIs. Route 53 is how traffic finds your application at all. These are the glue of serverless and event-driven AWS architectures.
SQS (Simple Queue Service) is a managed message queue: a producer puts messages in, one consumer pulls each message out and processes it. It smooths spikes (the queue absorbs bursts) and survives consumer downtime (messages wait). SNS (Simple Notification Service) is pub/sub: a publisher sends one message to a topic and every subscriber (Lambdas, SQS queues, emails, HTTP endpoints) gets a copy, fan-out. The common pattern is SNS fan-out into multiple SQS queues, so one event drives several independent workers. This is the AWS-managed version of the message-queue concepts from System Design.
API Gateway turns an HTTP request into a Lambda invocation and the Lambda's return into an HTTP response.
// Lambda handler behind API Gateway (HTTP API)export const handler = async (event) => {const userId = event.pathParameters?.id;const user = await getUser(userId); // your logicreturn {statusCode: user ? 200 : 404,headers: { "content-type": "application/json" },body: JSON.stringify(user ?? { error: "not found" }),};};// API Gateway handles: routing (GET /users/{id} -> this Lambda),// throttling/rate limits, API keys, auth (JWT / Cognito authorizers),// and CORS. You write the function; the gateway is the front door.// Pair with the API design lesson: versioning, pagination, idempotency still apply.
Route 53 is AWS's DNS service. Beyond plain domain-to-IP records, it does health checks and routing policies: latency-based (send users to the nearest region), weighted (send 10% of traffic to a new version for a canary), and failover (route to a backup when the primary is unhealthy). It integrates with the rest of AWS via alias records that point a domain straight at a CloudFront distribution, an S3 site, or a load balancer without hardcoding IPs. It is both where you register or manage the domain and how you steer traffic across regions and versions.
Calling a slow downstream service synchronously from a request path instead of dropping a message on SQS and returning immediately. Confusing SQS (one consumer per message, a work queue) with SNS (every subscriber gets a copy, fan-out). Using the wrong one breaks the design. Not configuring an SQS dead-letter queue, so poison messages retry forever. Forgetting API Gateway throttling/auth and exposing a Lambda to abuse and runaway bills. Hardcoding IPs instead of using Route 53 alias records, which break when the underlying resource's IP changes.
Pick the best design.
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