all #architecture#aws#backend#backend-engineering#billing#boto3#cloud#distributed-systems#django#dva-c02#event-driven#getting-started#iam#lambda#postgresql#python#s3#security#serverless#sns#sqs#system-design
Retries are guaranteed in distributed systems. Duplicate side effects are not. A deep dive into idempotency keys, the claim-first ledger pattern, and how to implement it in Django and PostgreSQL.
Synchronous, asynchronous, and poll-based invocation give the same Lambda code completely different failure modes, retry behavior, and scaling. A field guide to choosing, plus the three front doors for HTTPS: Function URLs, API Gateway, and ALB.
Both make your system asynchronous, but they solve different problems. Queue semantics vs topic semantics, when to reach for each, and the SNS → SQS fan-out pattern that shows up in real system designs.
Build the SNS-to-SQS fan-out pattern where each consumer owns a private queue with its own retry policy and DLQ. Covers queue policies, raw message delivery, redrive config, and the delivery guarantees you actually get.
A 25-minute walkthrough: create an AWS account, lock away the root user, create an IAM admin daily driver with MFA, and set billing budgets so you never get a surprise bill.
Why AWS won the cloud, what it looks like from a backend engineer's seat, and the one setup mistake almost every beginner makes on day one.
Upload files from the browser straight to S3 — no proxying through your backend. Presigned PUT URLs with Django, the s3v4 SignatureDoesNotMatch fix, and the exact CORS config you need.