Preventing Duplicate GraphQL Mutations with the Angular Service Worker and AWS Amplify

A GraphQL mutation gets executed twice on the server even though the client sent it once. The symptom pattern: two records with byte-identical payloads but different server-generated IDs, written 2 to 4 seconds apart by two separate resolver invocations. Only in production. Never reproducible on demand. If your Angular app registers @angular/service-worker and talks to AppSync through AWS Amplify, this is not a bug in your code. It is an interaction between two framework defaults.

Caching Amazon Athena Query Results with DynamoDB and Managed Query Results

Amazon Athena on Apache Iceberg is a natural fit for analytics dashboards, but every query carries a fixed overhead of one to several seconds, even when the result is a single number. Dashboards auto-refresh and get opened by many users, so the same queries run again and again, paying that latency and the scan bill every time. Athena ships a built-in Query Result Reuse feature, but it refuses to run in a workgroup that uses Managed Query Results.

Serving Tenant-Branded, Login-Free Web Pages from a Lambda with Tokenized Access

A recipient needs to open a document you sent them. They have no account, and you do not want them to create one. The document is sensitive, for example a medical report, so it must be delivered in the sender's branding, it must reflect the current state of the case, and it must be revocable the moment something changes. A static link cannot do all three at once.

Multi-Tenant HTTP API with Clean Custom Domains, Wildcard Certificates and Account Slugs

A default HTTP API on AWS exposes an unusable URL such as a1b2c3d4.execute-api.eu-central-1.amazonaws.com.
In multi-tenant environments you want stable, human-readable, tenant-specific URLs that integrate cleanly into your product.
This guide shows how to build exactly that using a wildcard certificate, a custom domain, Route53 alias records and SSM-based account identity.

Puppeteer PDF Page Numbers with Header and Footer Templates

HTML-to-PDF rendering fails once multi-page layouts, dynamic content, and page numbers are involved. Puppeteer can generate PDFs out of HTML-templates with stable page numbers, but only when its header and footer templates are used correctly.

Following you will find a working approach for dynamic multi-page PDFs with clean page numbers using NodeJS Chromium Puppeteer's header and footer templates.