Stack InsideFeatured · Backend
Internal admin panels start as “just a page to refund that order” and become the highest-privilege service you run—often with weaker auth than customer login. Attackers know this. So do bored employees. A minimal admin can be safe if you treat it as production security work, n...
Backend · Security
Internal admin panels start as “just a page to refund that order” and become the highest-privilege service you run—often with weaker auth than customer login. Attackers know this. So do bored employees. A minimal admin can be safe if you treat it as production security work, n...
Performance · Reliability
“We hit 10k RPS in staging” is not a result. It is a party trick if the question was never written down. Useful load testing starts with a **decision**: ship, change pool size, buy capacity, or stop a release. This article frames one question, sets criteria first, then uses a...
Security · Backend
Secret rotation fails when only one value is valid at a time and instances roll slowly. The safe pattern is **overlap**: accept old and new during a window, then drop old. This article shows that dual-read pattern with a tiny lab and a deploy order you can reuse for API keys,...
Databases · Migrations
Schema changes on hot tables fail in two popular ways: a blocking `ALTER` that stalls writes, or a deploy that reads a column the database does not have yet. Online-safe migrations are mostly **ordering discipline**—expand, dual-write or backfill, contract—not clever one-liners.
Backend · Distributed systems
Systems do not get infinite memory when traffic spikes. If you accept every request into an unbounded queue, you trade a quick 429 for a slow death—GC thrash, stale work, and timeouts that all arrive later together. Backpressure is the decision to **refuse or delay work early*...
Backend · Release
Feature flags are often sold as experimentation. In production backend systems their highest value is a **kill switch**: turn off a dangerous path without rebuilding binaries under stress. That only works if evaluation order is correct, defaults are safe, and someone owns clea...
Databases · Migrations
Database cutovers fail for social reasons as often as technical ones: unclear ownership, no rollback criteria, and “we will watch dashboards” without a written abort line. This article is a **checklist you can paste into a runbook** for moving traffic between database endpoint...
Backend · Observability
Timeouts often arrive without a stack trace. The client sees 504, the load balancer says upstream timed out, and your process is still healthy enough to answer `/healthz`. Local CPU flame graphs look fine. The useful question is not “why is Node broken?” but **which hop spent...
Backend · APIs
Payment providers and internal webhooks retry. They retry because your endpoint timed out, because their network blipped, or because their policy says “at least once.” If your handler charges, ships, or emails on every delivery, duplicates become customer-facing bugs. Idempote...
Backend · Caching
Caching is a performance tool, not a default layer for every read. Used in the wrong place it serves stale prices, stampedes the database when TTLs align, or hides an unaffordable query until the day the cache is cold. This article walks three failure modes with a small Node l...
15/15 published · calendar
Original essays by Cole and Jerry. Each topic aims for first-hand evidence—labs, plans, configs, or checklists. See the updates log for what shipped and what is scheduled next.
Backend · Observability · published
Walk one real incident from first alert to root cause using logs, metrics, and a narrow reproduction—not a generic debugging checklist.
Databases · Migrations · published
A field checklist from a real cutover (or dry-run on a copy), including rollback and data-diff steps—not a vendor migration brochure.
Backend · Kubernetes · published
Show a service that returned 200 while unable to serve traffic, and the readiness design that fixed it.
Backend · APIs · published
Design and implement idempotency for one concrete callback flow you own, including duplicate delivery tests.
Databases · Performance · published
Derive pool size from real concurrency, not blog defaults. Include a near-miss or outage where pools exhausted the DB.
Observability · Backend · published
Before/after log samples from a service you run, and the fields that made an incident diagnosable in minutes.
Backend · Release · published
How you use flags to ship and abort safely, including a flag that saved a release—or one that caused confusion.
Backend · Distributed systems · published
One pipeline or API where load exceeded capacity, and the concrete backpressure path you implemented.
Databases · Migrations · published
One migration you shipped online (expand/contract or tool-assisted), with timing and lock risks called out.
Backend · Caching · published
Counter-intuitive cases from your systems where removing or narrowing cache fixed correctness or latency.
Databases · MySQL · published
Single slow query, full EXPLAIN (or EXPLAIN ANALYZE) walkthrough, index or rewrite that fixed it, with before/after timings.
Incidents · Operations · published
Template shaped by real postmortems you ran; show one anonymized filled example.
Security · Backend · published
Rotate one real secret class (DB password, API key, JWT signing key) with overlapping validity.
Performance · Reliability · published
One load test you designed around a business risk, not a vanity RPS number.
Backend · Security · published
Ship a small internal tool with authz, audit log, and dangerous-action guards from day one.