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A background worker sits quietly for weeks, chewing through a job queue without incident, and then one Tuesday afternoon it disappears mid-batch, taking forty in-flight jobs down with it. No stack trace pointing at the offending line, no alert until a customer notices their export never finished. Nine times out of ten, the culprit is one of the most under-discussed failure modes in server-side JavaScript: unhandled promise rejections. They are easy to introduce, easy to miss in code review, and in modern Node.js they no longer just print a warning — they can end your process outright. This post walks through what unhandled promise rejections actually are at the engine level, why they are far more dangerous in long-running Node.js services than in typical web requests, how Node's default behavior around them has shifted over the years, and the concrete patterns you can use to stop them from quietly killing your jobs. What an Unhandled Promise Rejection Actually Is At the JavaScript engine level, a promise is a state machine with three possible states: pending, fulfilled, or rejected. When an async operation fails — a network call times out, a database query throws, a JSON parse blows up — the promise representing that operation transitions to the rejected state and carries a reason, usually an Error object. That's all a rejection is: a value flowing down the promise's error channel instead of its success channel. The engine only considers a rejection "handled" if, by the time it does its bookkeeping (which happens on a microtask checkpoint, not synchronously), there is a .catch() handler, a second argument to .then() , or a surrounding try/catch around an await somewhere in that promise's chain. If none of those exist anywhere in the chain, the rejection is classified as unhandled. This is the precise, narrow definition of unhandled promise rejections: a promise that reaches the rejected state with zero handlers attached anywhere along its chain of consumers. It's wo

An AI can write a perfect email in seconds. Having a real back-and-forth conversation is much harder. Sarah runs a salon. She has an AI assistant that emails her customers when a slot opens up. Last Friday, a customer canceled his booking. The assistant sent an email: "We have an opening tomorrow at 2 PM. Want it?" The customer replied in a minute: "Yes, book it!" The assistant never saw that reply. The slot stayed open. The customer never got a confirmation. This happens more than people realise — not because it's hard to receive email, but because most setups were never wired to close the loop. Sending is easy. Wiring the whole loop isn't. To be fair, receiving and parsing email isn't some unsolved problem — providers like SendGrid, Mailgun, and Postmark have offered inbound email parsing for years. Point your domain at them, and they'll hand you the clean message. But those webhooks only push the message once. There's no inbox to check back later, and no built-in way to link a reply to the right conversation. You have to build that part yourself — and you still can't run any of it on your own servers. There's a second issue too. AI assistants sometimes send a slightly odd reply — nothing harmful, just a little off. Many managed email providers watch for exactly that pattern, and can suspend an account fast. One strange sentence, and Sarah's whole booking system could go dark with no warning. What a real AI assistant needs For an assistant like Sarah's to actually hold a conversation, a few things need to work together: Replies need to land somewhere the AI can read them They need to arrive clean, not messy They need to stay linked to the right conversation The AI needs to reply back from the same email address All of it needs to run on infrastructure you control, not three different vendors This is what we built Reloop for Reloop puts that whole loop in one place, self-hosted. When Sarah's customer replied "Yes, book it!", Reloop caught the reply, cleaned it up,

Building Profitable Niche Lifestyle Stores: A Developer's Guide to E-Commerce Essentials Launching a niche lifestyle e-commerce store is more than just setting up a storefront—it's a technical challenge that requires thoughtful architecture, performance optimization, and strategic content planning. Whether you're building a store for outdoor gear, fashion accessories, or humor products like humor24.se , here's what developers need to know. Choose the Right Tech Stack Most profitable niche stores run on WordPress + WooCommerce + a performance-focused theme (like Blocksy). This combination offers: Flexibility : Extend functionality without rewrites SEO-friendly : Built-in structured data support Cost-effective : No complex deployment infrastructure needed Content integration : Blog + products on the same platform Use a headless CMS approach only if you have compelling reasons (high-traffic requirements, complex frontend needs). For 99% of niche stores, the overhead isn't worth it. Core Web Vitals = Revenue Google's Core Updates consistently penalize slow stores. Prioritize: LCP (Largest Contentful Paint) < 2.5s : Optimize images (WebP/AVIF format), lazy load below-fold content, defer non-critical CSS INP (Interaction to Next Paint) < 200ms : Minimize main thread blocking, defer JavaScript CLS (Cumulative Layout Shift) < 0.1 : Use fixed image dimensions, avoid late-loading ads/widgets # Generate WebP variants of product images convert image.jpg -quality 80 image.webp # Check your Core Web Vitals # Use PageSpeed Insights API or Lighthouse CI in your deployment pipeline Each 0.1s improvement in LCP can yield 3-5% conversion uplift. Performance is a feature. Structured Data Wins Traffic Rich snippets dramatically improve click-through rates. Implement: Product schema : name , price , availability , image , brand , AggregateRating BreadcrumbList : Navigation structure FAQ schema : If you have FAQs (47% higher CTR for FAQ snippets) { "@context" : "https://schema.org/" , "@t

As a backend developer, I have build hundreds of endpoints, so the typical endpoint flow is deeply ingrained in how I think about web applications. But when I started building AI-powered endpoints, I noticed an interesting shift. At first, AI endpoints looked like simple proxy endpoints with some configuration for connecting to a model: API receives request ↓ send prompt to model ↓ receive response ↓ return it to the client And it worked well until I found out that passing a prompt directly from the client was not a good idea. The endpoint could be misused for a completely different purpose, allowing someone else to consume my AI usage credits. Then I realized that the input also needed limits. Sending a large context for a specific task costs more and may produce unexpected results. So when I started looking closer, especially when I needed reliable structured output and predictable application behavior, I quickly realized that it was not that simple. Validation was no longer only guarding execution, it had also become a post-processing step. AI models are probabilistic. Even with the same input, they may return different outputs, omit required information, misunderstand instructions or return something that is technically valid but logically wrong. And because every token has a price, I cannot simply retry the request and hope for a better result. That was when I started questioning whether AI endpoints should be designed in the same way as conventional Web API endpoints. Table of Contents Conventional Web API Endpoint Flow AI-powered Web API Endpoint Flow What This Difference Changes Unpredictable Latency Retry Logic Idempotency and Side Effects Testing AI Endpoints The Output Contract Observability and Cost Summary Conventional Web API Endpoint Flow A conventional Web API endpoint usually follows a similar flow: validate request ↓ execute business logic ↓ return representation The first phase is request validation. We validate the incoming data against property

Next.js 16 shipped Cache Components - the feature that finally lets a single route mix static HTML, cached data, and per-request dynamic content without splitting it into separate pages. It is Partial Prerendering (PPR) made stable, plus a new use cache directive that replaces the old unstable_cache and the awkward route-segment config flags. This guide covers what changed, the three content types you now think in, and the runtime-data rule that trips up almost everyone on day one. What actually changed If you were using the experimental PPR flag, it is gone. Cache Components is a single config switch, and it turns on the whole model - static shell, cached segments, and streamed dynamic content in one route. // next.config.ts import type { NextConfig } from ' next ' const nextConfig : NextConfig = { cacheComponents : true , // replaces experimental.ppr } export default nextConfig Once it is on, every piece of your route falls into one of three buckets. The whole mental model is learning which bucket each component belongs in. The three content types Static - synchronous code, imports, and pure markup. Prerendered at build time and served instantly from the CDN. Your header, nav, and layout shell. Cached - async data that does not need to be fresh on every request. Marked with use cache . Think product lists, blog posts, dashboard stats. Dynamic - runtime data that must be fresh (cookies, headers, per-user state). Wrapped in Suspense so it streams in after the shell paints. import { Suspense } from ' react ' import { cookies } from ' next/headers ' import { cacheLife } from ' next/cache ' export default function DashboardPage () { return ( <> { /* Static - instant from the CDN */ } < header >< h1 > Dashboard </ h1 ></ header > { /* Cached - fast, revalidates hourly */ } < Stats /> { /* Dynamic - streams in with fresh data */ } < Suspense fallback = { < NotificationsSkeleton /> } > < Notifications /> </ Suspense > </> ) } async function Stats () { ' use cache ' cacheL

Most developers think about crypto payments as a checkout problem. Generate an invoice. Show a payment page. Wait for a webhook. Mark the order as paid. That is the clean version. Real merchants do not live in the clean version. They live in support tickets. A customer says they paid, but the order is still pending. A payment arrives after the invoice expires. Someone sends the right amount on the wrong network. A webhook fails. A customer underpays. A support agent cannot tell whether the issue is customer error, blockchain delay, invoice expiry, fulfillment failure, or an internal system bug. This is where developers can build a real product. A Crypto Payment Support Desk is a support and operations layer for merchants that accept crypto payments. It helps support teams search payments, inspect payment timelines, classify issues, explain statuses to customers, escalate real problems, and reduce the amount of manual investigation required for every crypto payment ticket. In this article, I will use OxaPay as the example payment infrastructure because its documentation exposes the primitives needed to build this kind of product: invoice generation, payment status callbacks, HMAC-signed webhooks, payment information lookup, payment history, static addresses, SDKs, plugins, and automation integrations. This is not a generic “add crypto payments to your app” article. It is a blueprint for developers who want to build a support-facing product that merchants may actually pay for. The business idea The idea is simple: Build a support desk that sits between a merchant's payment system, order system, and support team. The merchant already accepts crypto payments. The problem is that their support team cannot quickly answer payment-related questions. Your product gives them one place to investigate cases like: “The customer says they paid, but the order is unpaid.” “The invoice expired, but a transaction later appeared.” “The payment is underpaid.” “The webhook was received,

Meta's React library has integrated a Rust version of the React Compiler into its main repository, aimed at enhancing build speed and compatibility with the Rust-based JavaScript toolchain. This port, which memoizes components automatically, demonstrates significant performance improvements, boasting up to 50% faster compilation. The public API remains unchanged to facilitate easy upgrades. By Daniel Curtis

Nowadays, web frameworks come with ✨ magic ✨. Some more than others, but all of them have some. The...

If you're building an app that generates the same character across many scenes, you've probably hit the wall already: seeds drift, LoRA training is heavy and slow, and "same character, new pose" prompting quietly changes the face. The approach that actually holds up in production is a 2-stage pipeline — generate one canonical base image , then edit from that base as the reference for every new scene. Consistency comes from the reference, not the seed. Below: why the common approaches drift, how the 2-stage pipeline works, the async job queue that makes it deployable, and the serverless-GPU setup that keeps it affordable. There's a free, runnable slice of the whole transport layer at the end. Why the obvious approaches drift Seeds. A seed pins the noise , not the identity . Re-use a seed with the same prompt and you get the same image — but that's reproduction, not consistency. The moment you change the prompt ("now she's in a café"), the denoising path changes and the face re-rolls with it. Seeds give you determinism for identical inputs; they give you nothing for new scenes . Prompt-only ("the same woman as before"). The model has no memory. Every generation is a fresh sample from the distribution your words describe. "Same face as last time" isn't in the prompt vocabulary — there is no last time. LoRA per character. This one actually works — that's why everyone suggests it — but look at what it costs in an app context: curate 15–40 images per character, run a training job per character, store and load adapter weights per character, and repeat all of it whenever a user creates someone new. For a personal project, fine. For an app where users create characters on demand, you just signed up to run a training farm. The 2-stage pipeline The fix is embarrassingly direct once you see it: Stage 1 — CAST Stage 2 — RE-SCENE (repeat forever) text-to-image image-edit model "describe character" → base image + "put them in a café" → scene 1 = base image base image + "walking in

Hello, I'm Maneshwar. I'm building git-lrc, a Micro AI code reviewer that runs on every commit. It is...

Two lines of code. Same variable. Same operator. Completely different behavior. a = [ 1 , 2 , 3 ] b = a b += [ 4 ] # line A print ( a ) # [1, 2, 3, 4] x = 1 y = x y += 1 # line B print ( x ) # 1 Line A changes a . Line B does not change x . The only difference is whether the variable holds a mutable or immutable object. To understand why this happens, you need to understand how Python actually represents variables internally. Variables Are Not Boxes The box metaphor is how most introductory programming courses explain variables: a variable is a box that holds a value. You put 5 into the box called x . Later you can replace it with 10. In Python this metaphor is accurate for immutable types and dangerously misleading for mutable types. The more accurate model: a Python variable is a name that is bound to an object. The object exists independently of the name. Multiple names can be bound to the same object. Binding a name to a new object does not affect the old object or other names that reference it. You can inspect this directly: a = [ 1 , 2 , 3 ] b = a print ( id ( a ) == id ( b )) # True -- same object, two names x = 5 y = x print ( id ( x ) == id ( y )) # True -- both point to integer object 5 Both cases start the same: two names pointing to the same object. What happens next depends on whether you mutate the object or rebind the name. Two Fundamental Operations Every operation on a Python object falls into one of two categories. Mutation : the object at a given memory address is modified. All names pointing to that address see the change. Rebinding : a name is pointed at a different memory address. Other names pointing to the original address are unaffected. List methods like .append() , .extend() , .sort() , and item assignment lst[i] = x are mutations. Assignment with = is rebinding. The += operator is either mutation or rebinding depending on whether __iadd__ is implemented and the object is mutable. Tracing Through the Object Graph a = [[ 1 , 2 ], [ 3 , 4 ]]

Remember the days when we used to dump all our CSS and JavaScript into a single index.html file? That's exactly what a "Mega-Prompt" is today: an unmanageable monolith. A few weeks ago, while working on the orchestration of Vibrisse Agent (my local AI agent), I hit this exact wall. I was trying to stabilize a complex task by adding instructions to a 500-line system prompt. The more rules I added, the more the model forgot the older ones. The industry has sold us the myth of the Mega-Prompt. Those famous "50 ultimate prompts" or massive blocks of incantatory text are a technical dead end. Creative writing doesn't scale in production. As a web developer, my conviction is simple: to build reliable applications, we must stop "talking" to the machine and start configuring it. This is the shift from Prompt Engineering to Context Engineering . Context Engineering: Typing and Structure The first mistake with LLMs is mixing instructions (the logic) and context (the data) into an unstructured stream of text. It's the cognitive equivalent of spaghetti code. The solution? A strict separation of concerns. A highly effective technique (documented by Anthropic, but applicable to any model, including local SLMs), is XML Tagging . Here is the "dirty" approach (classic chat): You are a security expert. Analyze this authentication code, be strict, don't write a summary, check for XSS and SQLi vulnerabilities. Here is the code: function login() { ... } And here is the "engineering" approach: <role> Application Security Expert </role> <instructions> 1. Analyze the code provided in <context> . 2. Identify vulnerabilities (focus: XSS, SQLi). 3. Do not produce an introductory summary. </instructions> <context> function login() { ... } </context> Typing the language via tags creates clear boundaries. The model knows exactly where the directive is and where the data is. The Power of Exemplars (Few-Shot Prompting) Even with clear instructions, AI can drift in output format or tone. This is wh

After spending 2 years building an image compression tool, here's my no-nonsense format guide. ## The Rule | If it's... | Use... | |---|---| | Logo, icon, screenshot | PNG | | Photo, everyday image | WebP | | Smallest possible file | AVIF | | Maximum compatibility | JPEG | ## Why? PNG — Lossless. Keeps text and sharp edges crisp. Supports transparency. But files are large for photos. JPEG — Works literally everywhere since 1992. Good compression for photos. No transparency support. At 80-85% quality, the visual difference from 100% is invisible but the file is half the size. WebP — The sweet spot. 25-35% smaller than JPEG with same quality. Supports both lossy and lossless. Supports transparency. Every modern browser supports it now (97%+ global coverage). For most websites, this is the right answer. AVIF — The next-gen format. 50% smaller than JPEG, 30% smaller than WebP. Supports HDR, 12-bit color, and both lossy/lossless. The catch: not supported on older devices (iOS 15 and below). Use it with a <picture> fallback. ## Real Numbers I ran the same photo through all four formats at comparable quality: JPEG (90%): 842 KB PNG: 3,241 KB WebP (90%): 547 KB AVIF (90%): 382 KB WebP cut the JPEG size by 35%. AVIF cut it by 55%. ## What I Recommend I built CompressFast ( https://compressfast.site ) — a free browser-based image compressor that handles all these formats. No uploads, no servers, everything runs locally.

TL;DR Spent today rebuilding two training diagrams — a layered reference architecture and a workflow swimlane — as single-file HTML instead of exported images. The trick: data in a plain JS array, layout in CSS Grid, connectors in an SVG overlay measured at runtime . Result: diagrams you can step through, click into, and hand over as one file that opens offline. Why not just export a PNG? Because a screenshot is stale by the next sprint, and nobody re-opens the drawing tool to fix it. Approach Editable by a dev Interactive Portable PNG from a drawing tool No (need the source file) No Yes Mermaid in a doc Yes No Needs a renderer Hand-built HTML Yes (it's a data array) Yes One file, opens anywhere The third option costs a few hours once. After that, updating a component is editing one object in an array. Separate the data from the drawing This is the whole design. Nothing about position, colour, or DOM lives in the content: const TIERS = [ { key : ' clients ' , label : ' Clients ' , sub : ' consumers · admins ' }, { key : ' edge ' , label : ' Edge ' , sub : ' TLS · load balancing ' }, // ... ]; const COMPONENTS = [ { id : ' app ' , tier : ' app ' , x : . 34 , label : ' Control Plane ' , tech : ' PHP-FPM ' , role : ' Governance UI and sync orchestration. ' , points : [{ type : ' info ' , text : ' Pushes approved config downstream ' }] }, // ... ]; const LINKS = [[ ' consumers ' , ' edge ' ], [ ' edge ' , ' gateway ' ], /* ... */ ]; tier picks the row. x is a fraction (0..1) across that row , not a pixel. So the layout survives any viewport without me hand-tuning coordinates. Layout: Grid for the boxes, SVG on top for the wires +--------------------------------------------------+ | lane label | [card 1] [card 2] [card 3] | <- CSS Grid row |------------+-------------------------------------| | lane label | [card 4] [card 5] | +--------------------------------------------------+ ^ ^ sticky column SVG overlay (position:absolute; inset:0) draws paths between measured centre

GitHub redesigned GitHub Issues navigation using a client-side architecture that combines caching, predictive prefetching, and service workers to reduce perceived latency. The approach uses IndexedDB, in-memory caching, and background synchronization to serve data faster. GitHub reported instant navigation improvements from 4% to 22%, with latency reductions across multiple navigation By Leela Kumili

I spent months building an AI agent platform. I launched it on Product Hunt yesterday. Zero signups. The comments were friendly. Three of the four asked for the same thing — not features, not integrations, not a lower price. They wanted to see what the agents did and what they cost . One put it better than my own landing page ever did: they liked that it wasn't "a black box." So I went to make the cost dashboard better. Instead I found out my product had been lying to me for months, and the lies had a pattern. Here's everything, with the code. 1. Every run cost $0.00 The Cost Analytics page reported $0.02 in total across ~100 executions . I'd assumed that meant the platform was cheap to run. It meant the data was being destroyed at write time. cost_cents = int ( ( llm_response . prompt_tokens * 0.5 / 1000 ) + ( llm_response . completion_tokens * 1.5 / 1000 ) ) A typical run on my platform is 56 prompt tokens and 45 completion tokens. That's 0.0843 cents . int() makes it 0 . Not some runs. Essentially every run — because almost every LLM call costs less than one cent. The production numbers: 189 agent runs, 2 with a non-zero cost. 99% of my cost data was zeroes, and the two survivors were just big enough to clear a whole cent. The rates in that formula were correct. I checked them against the providers' pricing pages; the arithmetic is right. The bug is entirely int() on a value that is almost never ≥ 1. A Decimal would have been the textbook fix, but Decimal / float raises TypeError and ~80 call sites do arithmetic on this number, so I widened the column to a float and kept the unit (cents). It's a dashboard estimate, not money — Paddle handles money — so float rounding is irrelevant here. 2. Workflow costs were never recorded at all Truncation at least loses precision. This one lost everything. WorkflowExecution.total_cost_cents and total_tokens_used had no write site anywhere in the codebase . Not a broken write — no write. The columns had been NULL since the feat

A customer clicks the Pay button, the server sends the request to a payment provider, and the charge succeeds. The trouble begins when the response never reaches the browser because the connection drops. The frontend sees a timeout and retries the same request, while the backend treats it as a brand-new payment. One customer action has now created two valid charges. This kind of failure is easy to miss because every part of the system appears to behave correctly on its own. The browser retries because it never received a response, the API processes a valid POST request, and the payment provider accepts the instruction it was given. The defect sits between those systems, where no component has enough context to know that the second request is a repeat. The same pattern can create duplicate orders, emails, subscriptions, shipments, support tickets, or background jobs. The common advice is to retry failed requests, but that advice is incomplete. A retry is safe only when the server can distinguish a repeated business operation from a new one. For payment APIs, that usually means introducing an idempotency key, storing the original result, and protecting the write path against race conditions. The rest of this article walks through that flow using Node.js, Express, and PostgreSQL. The bug starts with a normal-looking endpoint Consider a small Express endpoint that creates a payment by calling an external provider. The code receives the request body, sends the amount and customer data to the provider, and returns the resulting payment object. Nothing about this route looks obviously unsafe during a basic code review, and the happy-path test is likely to pass without trouble. The risk appears only when the request succeeds remotely but the response is lost before the client receives it. `app.post("/payments", async (req, res, next) => { try { const payment = await paymentProvider.charge({ customerId: req.body.customerId, amount: req.body.amount, currency: req.body.currenc

This week I accidentally created my first vibe coded application. You might ask how one does this accidentally, but it's actually easier than you think. Assumptions Made: The first mistake I made was to assume that Claude remembered my setup and how I like to pair program. I have only had one previous project coded with the help of Claude and GHCP and it's a much more basic application than what I was building this week. I assumed, incorrectly, that Claude would 'remember' how I liked to work and go through the project with me as we make decisions and coding blocks together. The other assumption I made was giving a somewhat blanket approval for Claude to just run with things. I thought at some point Claude would stop, check its understanding during development and then continue but I got excited at the idea of using subagents and once I'd selected that option there was no stopping Claude on its rampage through my code! So What's the Project? I've recently started looking at doing more work with AI rather than just prompting Claude or GHCP to help with the day to day. I wanted to actually call an LLM and sift through information which could then be saved in a DB and recalled at a later point. I set myself a four week plan (with the help of Claude) to help solidify my learning with week one being a basic console application in C# that takes some text, sends to an LLM and then extracts certain information, in this case names of people, which is saved into a Postgres database. Sounds simple right? Where things went right This project started off very interesting. I had a conversation with Claude, same as I would with another developer, about the right LLM to use for this project. We went through the positives, negatives and the potential cost benefits and pitfalls of each option. In the end it was narrowed down to two choices, OpenAI or Gemini. Given that I was experimenting quite a bit and I didn't want to accidentally run up costs, I decided to go with Gemini's free t

A configuration change in AWS's bill computation system showed customers estimated bills in the billions and trillions of dollars for over 24 hours. AWS's own alarms detected the anomalies but failed to halt bill generation or page engineers; customer escalations alerted the company 4.5 hours later. Budget and cost anomaly alerts were disabled platform-wide during mitigation. By Steef-Jan Wiggers

Finished up a solid coding sprint tonight working on Safi-Budget a financial management application built around the 50/30/20 budget framework. I'm currently building and training over at Zone01Kisumu , and getting this build updated and deployed live was the main goal for today's session. What Was Updated Today Localized Currency Logic: Updated the core engine defaults from EUR over to** KES** (Kenyan Shillings) to better support local financial tracking workflows. Auth Flow Refinements:** Ironed out session management and routing logic to ensure clean sign-in and logout behavior across the app. Containerization & Deployment:** Confirmed the Go backend containerizes smoothly with Docker and runs cleanly on Render. Tech Stack Language: Go (Golang) Containerization: Docker Deployment Platform: Render Live Demo & Link You can test out the live deployment here: 👉 Safi Budget Engine Live App