Technical Notes

Browse technical notes, course breakdowns, and debugging writeups organized by topic.

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accessibility ACID Agent Skills agents AI AI agents AI tools algorithms API API design array Astro async B-tree backup Blind 75 browser APIs bucket sort caching capability security cardinality CDN Claude Code cloud deployment Cloudflare Cloudflare Workers Codex complexity analysis concurrency connection pooling constraints Containers Content Security Policy context engineering CSP CSS CSS Overflow 5 data modeling database deployment disaster recovery distributed systems dynamic programming Dynamic Workers frequency counting Git hash table House Robber HTML HTTP hydration idempotency index indexing intervals interview preparation JavaScript job queue JOIN learning LeetCode LLM machine learning Map MCP MCP Apps merge multi-tenancy Next.js normalization observability pagination performance PgBouncer PITR PostgreSQL prefix product prefix sum prerendering primary key production observability progressive enhancement python query query design query performance query planner React Server Components rebase recursion retries rolling state Row-Level Security schema migration security security headers SELECT serverless Set sliding window sorting SPA SQL SSR static site string suffix product Supabase testing token efficiency transaction two pointers TypeScript UI UUIDv7 verification version control View Transitions web development web performance web security Workers workflow XSS zero downtime

PostgreSQL backups: what pg_dump, WAL, and PITR actually do

#PostgreSQL#database#backup+2

2026-10-07

Supabase RLS Beyond the Policy UI: Make Authorization SQL Testable

#Supabase#PostgreSQL#Row-Level Security+2

2026-09-18

PostgreSQL RLS is not an automatic WHERE clause: four boundaries for multi-tenant data

#PostgreSQL#database#security+2

2026-09-17

PgBouncer does not make PostgreSQL infinite: budget connections before choosing a pool mode

#PostgreSQL#database#connection pooling+2

2026-09-16

LeetCode 198: House Robber with take-or-skip rolling states

#LeetCode#Blind 75#TypeScript+4

2026-09-15

LeetCode 70: Climbing stairs from repeated recursion to two rolling states

#LeetCode#Blind 75#TypeScript+4

2026-09-14

A retry is not a second attempt: the real boundaries of API idempotency keys

#API#idempotency#retries+2

2026-09-14

LeetCode 152: Why maximum product subarray needs both extremes

#LeetCode#Blind 75#TypeScript+3

2026-09-11

LeetCode 53: Maximum subarray without rescanning every starting point

#LeetCode#Blind 75#TypeScript+3

2026-09-10

LeetCode 238: Product of array except self with prefix and suffix products

#LeetCode#Blind 75#TypeScript+3

2026-09-09

Why does the next page repeat a row? OFFSET and keyset pagination

#PostgreSQL#database#pagination+1

2026-09-09

ArtInt Reading Notes: Intelligent Agents and the AI Basics I Mixed Up

#AI#learning#agents+1

2026-09-08

The site is deployed. Why am I still seeing the old version?

#HTTP#caching#CDN+1

2026-09-08

LeetCode 15: 3Sum in TypeScript, Why Skipping Duplicates Does Not Lose Answers

#LeetCode#Blind 75#TypeScript+3

2026-09-07

LeetCode 11: Container With Most Water in TypeScript, Why Move the Shorter Side?

#LeetCode#Blind 75#TypeScript+4

2026-09-06

LeetCode 125: Valid Palindrome in TypeScript, From Cleaning to In-Place Two Pointers

#LeetCode#Blind 75#TypeScript+5

2026-09-04

Don't block first: use CSP Report-Only to find real dependencies, then tighten safely

#CSP#Content Security Policy#web security+2

2026-09-04

LeetCode 424: Longest Repeating Character Replacement in TypeScript

#LeetCode#Blind 75#TypeScript+5

2026-09-03

LeetCode 3: Longest Substring Without Repeating Characters in TypeScript

#LeetCode#Blind 75#TypeScript+5

2026-09-02

A schema migration is not one SQL statement: expand, backfill, and observe before you contract

#PostgreSQL#database#schema migration+2

2026-09-02

LeetCode 49: Group Anagrams in TypeScript, From Sorting Keys to Count Signatures

#LeetCode#Blind 75#TypeScript+5

2026-09-01

LeetCode 347: Top K Frequent Elements in TypeScript, From Frequency Sorting to Buckets

#LeetCode#Blind 75#TypeScript+5

2026-09-01

LeetCode 242: Valid Anagram in TypeScript, From Sorting to Character Counts

#LeetCode#Blind 75#TypeScript+5

2026-08-31

Do not add an index first: use EXPLAIN, statistics, and ANALYZE to see what PostgreSQL is guessing

#PostgreSQL#database#query performance+2

2026-08-31

LeetCode 1: Two Sum in TypeScript with a Map

#LeetCode#Blind 75#TypeScript+5

2026-08-30

LeetCode 217: Contains Duplicate in TypeScript with a Set

#LeetCode#Blind 75#TypeScript+5

2026-08-29

LeetCode 121: Best Time to Buy and Sell Stock in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-28

Indexes follow query shape, not a column checklist

#PostgreSQL#database#index+2

2026-08-28

Transaction Boundaries for Orders, Inventory, and ACID

#PostgreSQL#database#transaction+2

2026-08-27

LeetCode 2574: Left and Right Sum Differences in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-26

LeetCode 724: Find a Pivot Index in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-26

LeetCode 1732: Find the Highest Altitude in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-25

LeetCode 1480: Running Sum in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-25

Before JOIN Syntax, Count the Relationship

#PostgreSQL#database#SQL+2

2026-08-25

LeetCode 128: Longest Consecutive Sequence in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-24

LeetCode 56: Merge Intervals in TypeScript

#LeetCode#TypeScript#algorithms+3

2026-08-24

A SELECT Needs Four Decisions: Columns, Rows, Order, Limit

#PostgreSQL#database#SQL+2

2026-08-24

A Database Is Not a JSON Blob: Let Constraints Protect Data

#PostgreSQL#database#SQL+2

2026-08-23

AbortController: Cancel Stale Work, Not Every Error

#browser APIs#JavaScript#async+1

2026-08-21

Navigation API: A Router Primitive, Not an SPA Mandate

#browser APIs#SPA#progressive enhancement+2

2026-08-20

Speculation Rules: Faster Navigation Must Not Do Things Early

#web performance#browser APIs#progressive enhancement+2

2026-08-19

Browser Scheduler: Classify Work Before You Queue It

#JavaScript#web performance#browser APIs+2

2026-08-18

MCP Tool Results: Decisions, Not API Dumps

#AI tools#MCP#AI agents+2

2026-08-17

<details> Is Disclosure, Not an Accordion System

#HTML#web development#accessibility+2

2026-08-16

Popover API: Less UI State, Not Free Accessibility

#HTML#UI#accessibility+1

2026-08-15

PostgreSQL SKIP LOCKED: Job Queue, Not Magic Broker

#PostgreSQL#database#concurrency+1

2026-08-14

Native CSS Carousels Are an Enhancement, Not a Rewrite

#CSS#web development#accessibility+2

2026-08-13

Cloudflare OS: Sandboxes Are Not the Security Model

#Cloudflare#AI agents#security+2

2026-08-12

PostgreSQL 18 Skip Scan: The Leftmost Rule, Revisited

#PostgreSQL#database#B-tree+2

2026-08-11

A Green Build Is Not a Live Release

#Astro#Cloudflare Workers#deployment+2

2026-08-10

MCP Apps Put UI in Chat, Not in Every Tool

#MCP#MCP Apps#AI tools+2

2026-08-10

Your SSR Data Is Part of the Page Weight

#Next.js#SSR#React Server Components+2

2026-08-09

View Transitions Make MPAs Smoother, Not SPAs

#View Transitions#CSS#web development+2

2026-08-07

Cloudflare Containers: When a Worker Is Not Enough

#Cloudflare#Containers#Workers+2

2026-08-06

UUIDv7 for Primary Keys: Better, Not Universal

#PostgreSQL#database#UUIDv7+2

2026-08-05

Agent Skills: Build Verifiable Workflows

#AI tools#Agent Skills#AI agents+2

2026-08-04

Caveman: Terse AI Agents, Same Accuracy

#LLM#AI tools#Claude Code+2

2026-04-13

Git Merge vs Rebase: Which Should You Use?

#Git#version control#merge+2

2026-01-08