Technical articles on backend architecture, blockchain systems, and software engineering.https://davidessien.dev/en-ushttps://davidessien.dev/blog/building-secure-jwt-auth-in-nestjs-argon2-redis-blacklisting-and-token-rotation-3gl9/https://davidessien.dev/blog/building-secure-jwt-auth-in-nestjs-argon2-redis-blacklisting-and-token-rotation-3gl9/Step beyond basic authentication tutorials and build a production-ready JWT flow in NestJS. This guide covers hashing with Argon2, managing token rotation, and implementing robust Redis blacklisting.Mon, 12 Jan 2026 00:00:00 GMThttps://davidessien.dev/blog/code-fingerprinting-detecting-duplicate-submissions-without-losing-your-mind-or-your-api-budget-307i/https://davidessien.dev/blog/code-fingerprinting-detecting-duplicate-submissions-without-losing-your-mind-or-your-api-budget-307i/While building a review system for algorithmic problem solutions, I needed a way to detect duplicate code submissions to save on API costs. Here is how I implemented efficient code fingerprinting.Tue, 02 Jun 2026 00:00:00 GMThttps://davidessien.dev/blog/handling-cold-starts-in-serverless-ai-why-your-first-request-fails-and-how-to-fix-it-527m/https://davidessien.dev/blog/handling-cold-starts-in-serverless-ai-why-your-first-request-fails-and-how-to-fix-it-527m/A technical analysis of cold start behavior in serverless AI infrastructure and practical mitigation strategies.Tue, 02 Dec 2025 00:00:00 GMThttps://davidessien.dev/blog/how-i-eliminated-19494-duplicate-mongodb-records-and-what-id-do-differently-today/https://davidessien.dev/blog/how-i-eliminated-19494-duplicate-mongodb-records-and-what-id-do-differently-today/One job listing. 19,495 MongoDB records. Here's how I found it, fixed it without downtime, and what a better migration looks like with hindsight.Sun, 12 Jul 2026 00:00:00 GMThttps://davidessien.dev/blog/how-to-authenticate-users-with-solana-wallets-in-nestjs-46gd/https://davidessien.dev/blog/how-to-authenticate-users-with-solana-wallets-in-nestjs-46gd/A comprehensive guide on implementing wallet-based authentication using Sign-In with Solana (SIWS) in a NestJS backend, including securely managing nonces in Redis to prevent replay attacks.Mon, 19 Jan 2026 00:00:00 GMThttps://davidessien.dev/blog/why-i-move-ai-model-calls-to-the-server-security-performance-and-everything-in-between-2dnh/https://davidessien.dev/blog/why-i-move-ai-model-calls-to-the-server-security-performance-and-everything-in-between-2dnh/When building an AI tool that reviews algorithmic code solutions, I quickly realized that making model calls directly from the client was a bad idea. This article breaks down why moving these calls to the server improves security, performance, and architecture.Tue, 26 May 2026 00:00:00 GMT