Codifly / Developer library
From judgment to code.
Guides to build and run products: architecture you can reason about, deployments you can repeat and operations that survive a retry. Every guide cites the documentation behind it.
Latest
Read. Try. Decide.
APIs & storage · 5 min01
Direct Uploads to S3: Presigned URLs Without Exposing Your Files
A secure presigned URL upload flow for S3: server-side authorization, per-tenant keys, quarantine, and object validation before you publish.
Sep 8, 2026Read guide
Semantic search · 5 min02
Embeddings and RAG: Design Retrieval Before the Prompt
A practical RAG guide: chunking, per-tenant filters, measuring recall@k, and migrating vectors without mixing incompatible embedding models.
Sep 8, 2026Read guide
Applied AI · 5 min03
How to Choose an LLM for Production Without Relying on Leaderboards
Choose an LLM for production with a real eval set, cost per accepted task, p50/p95 latency, and a safe fallback for when the model fails.
Sep 8, 2026Read guide
Backend & data · 5 min04
PostgreSQL: Find the Right Index with EXPLAIN
Read a PostgreSQL EXPLAIN plan, design a composite index for a real query, and add keyset pagination without breaking tenant isolation.
Sep 8, 2026Read guide
Distributed systems · 5 min05
Queues, Retries, and Idempotency: Stop Processing Messages Twice
Build idempotent queue consumers that survive duplicate messages, crashes between commit and ack, and poison messages without infinite retry loops.
Sep 8, 2026Read guide
Infrastructure as code · 9 min06
OpenTofu vs Terraform: When to Migrate Without Breaking Your Infra
Terraform and OpenTofu have diverged. When to switch, when to stay on HCP Terraform, and how to migrate one workspace at a time with an empty plan as proof.
Jun 8, 2026Read guide
By topic
The whole library
Deployment & CI/CD
5 guides- Environment variables and DATABASE_URL in production: a full guideWhat environment variables are, how your app reads them, the anatomy of DATABASE_URL and where to keep secrets without leaking them. Node and Python examples. 10 min · Jun 2, 2026
- Deploy Your App Fast Without EC2, VPC or IAM: A PaaS GuideWhen a PaaS beats hand-built EC2, VPC and IAM for shipping to production, and the compliance, network and scale signals that justify your own infrastructure. 8 min · May 29, 2026
- Why your build works locally but fails on deployYour build passes locally but fails on the server. The 10 most common causes (env vars, casing, versions, .gitignore, lockfile) and how to fix each one. 10 min · May 28, 2026
- Deploying a frontend from Git to AWSShip a frontend from your Git repository to AWS: private S3 behind CloudFront with OAC, or Amplify Hosting, with key-free GitHub Actions CI. 5 min · Jul 18, 2023
- Deploying a containerized HTTP service on AWSTake an HTTP service from your laptop to AWS: image in ECR, ECS on Fargate behind an ALB with health checks, rollback-safe deployments and scaling. 5 min · Jul 10, 2023
AWS & governance
4 guides- Separating environments (dev, staging, production) on AWSHow to separate dev, staging and production on AWS: accounts and OUs vs VPCs, naming, per-environment config and secrets, and artifact promotion. 5 min · May 7, 2026
- Granting an external platform least-privilege access to AWSHow to give an external platform access to your AWS account: a cross-account role with an external ID, least-privilege policies and IAM Access Analyzer audits. 5 min · May 6, 2026
- What is the best organizational structure for your AWS account?How to structure AWS with Organizations: a clean management account, OUs per environment and member accounts. Step by step in the console, CLI and Terraform. 12 min · Sep 12, 2023
- Connecting GitHub to AWS without access keys (OIDC)Deploy from GitHub Actions to AWS with OIDC and IAM roles instead of access keys, and grant read-only repository access with deploy keys or GitHub Apps. 5 min · Jul 18, 2023
DevOps & platform
3 guides- From DevOps to MLOps and platform engineering: what to learnWhich skills to prioritize to move from DevOps into MLOps or platform engineering and stay relevant as AI automates day-to-day operations. 8 min · May 25, 2026
- IT infrastructure trends that will define 2026IT infrastructure in 2026: AI-first design, edge, multi-cloud, AIOps, SLO-driven observability, zero trust and sustainability. What changes and where to start. 6 min · May 19, 2026
- The real challenges of DevOps and how to overcome themThe 11 most common DevOps adoption challenges, from cultural resistance to cloud cost, and concrete practices to overcome each one without slowing delivery. 7 min · May 19, 2026
Applied AI
2 guides- How to Choose an LLM for Production Without Relying on LeaderboardsChoose an LLM for production with a real eval set, cost per accepted task, p50/p95 latency, and a safe fallback for when the model fails. 5 min · Sep 8, 2026
- Coding agents in the enterprise: the challenge is infrastructureCoding agents already run real engineering tasks. The sandboxing, permissions, CI/CD and observability you need before letting one near production. 8 min · May 26, 2026
Architecture
2 guides- Infrastructure patterns that don't scale long-termSeven infrastructure patterns that work early on but create technical debt, operational risk and slower delivery as you grow, and how to fix each one in time. 8 min · May 19, 2026
- What is a load balancer? What it solves and what it doesn'tWhat a load balancer is and how it works: traffic distribution, health checks and failover, plus what it cannot fix in your app. Examples with AWS ELB. 8 min · May 19, 2026
Containers & Kubernetes
2 guides- Kubernetes Limits in Production: A Guide with Verifiable ThresholdsKubernetes limits to know before production: 110 pods per node, 5,000 nodes, etcd's 1.5 MiB request cap, 1 MiB Secrets, and how EKS, GKE and AKS differ. 10 min · May 26, 2026
- Dockerfile: consistent deployments on any cloudHow a Dockerfile packages your app with its dependencies so it deploys the same way locally, in staging and on any cloud. Best practices and ready examples. 9 min · May 19, 2026
Networking & DNS
2 guides- Delegating a subdomain to Route 53 without moving your domainDelegate a subdomain to Amazon Route 53 with NS records at GoDaddy, Namecheap or another provider, without migrating the parent domain, and verify it with dig. 5 min · Oct 17, 2023
- Link a GoDaddy, Namecheap or Google Domains domain to AWS Route 53Delegate DNS for a domain registered at GoDaddy, Namecheap or Squarespace (formerly Google Domains) to AWS Route 53 without transferring it or breaking email. 9 min · Sep 12, 2023
Observability
2 guides- How to Reduce Your Datadog Bill with OpenTelemetryDatadog bills per host, GB, span and custom metric. Cut costs with OpenTelemetry Collector routing, sampling, cardinality control and a hybrid stack. 10 min · Jun 4, 2026
- Poorly defined SLIs and SLOs: why they cause false alertsWhen SLIs track CPU instead of user experience, alerts turn into noise. Learn to define SLIs, SLOs and burn-rate alerts that fire only on real user impact. 9 min · May 19, 2026