Tutorials and guides on web app development, cloud, and deployment.https://kunalships.dev/https://kunalships.dev/articles/idempotency/idempotency-claim-first/https://kunalships.dev/articles/idempotency/idempotency-claim-first/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.Tue, 18 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/lambda-invocation/lambda-invocation-models/https://kunalships.dev/articles/lambda-invocation/lambda-invocation-models/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.Tue, 18 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/sqs-vs-sns-message-brokers-vs-pubsub/https://kunalships.dev/articles/sqs-vs-sns-message-brokers-vs-pubsub/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.Sun, 16 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/two-tier-fanout-sns-sqs/https://kunalships.dev/articles/two-tier-fanout-sns-sqs/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.Sat, 15 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/aws-account-setup-iam-admin-billing-budgets/https://kunalships.dev/articles/aws-account-setup-iam-admin-billing-budgets/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.Fri, 14 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/aws-for-python-developers-start-here/https://kunalships.dev/articles/aws-for-python-developers-start-here/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.Fri, 14 Aug 2026 00:00:00 GMThttps://kunalships.dev/articles/direct-browser-uploads-s3-presigned-urls/https://kunalships.dev/articles/direct-browser-uploads-s3-presigned-urls/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.Thu, 13 Aug 2026 00:00:00 GMT