NestJS Request Lifecycle Explained (with Cheat Sheet)
A complete guide to the NestJS request lifecycle: the exact order middleware, guards, interceptors, pipes, and filters run, and why it matters.
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A complete guide to the NestJS request lifecycle: the exact order middleware, guards, interceptors, pipes, and filters run, and why it matters.
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Designing Systems That Contain Failure — CS Week Perú 2026 On August 13, 2026, I had the opportunity to speak at CS Week Perú 2026 , an event organized by IEEE Computer Society student chapters across Peru. My session was: “Isolation and Trust Boundaries in Production: Designing Systems That Contain Failure” The talk explored how production systems can be designed to limit the impact of failures through explicit trust boundaries, architectural invariants, and evidence-based validation. The central idea was simple: The goal isn't to prevent every failure. The goal is to control its blast radius. Production systems fail. Requests overlap, processes crash, memory is exhausted, credentials can be compromised, and dependencies can become unavailable. Reliable engineering is not about assuming that none of these things will happen. It is about deciding what can be affected when they do . From Unit Tests to System Properties A green unit-test suite demonstrates that the tested units behave correctly under the conditions we defined. But it does not necessarily demonstrate that the system as a whole preserves its architectural properties under concurrency, multiple tenants, resource exhaustion, or real deployment conditions. A function can be correct in isolation while the system still violates an important invariant. That led to one of the central questions of the talk: What properties must never be violated? Trust Boundaries I used the concept of a Trust Boundary to make architectural assumptions explicit. For each boundary, we can ask three questions: What are we protecting? What is allowed to cross the boundary? What happens if the condition is violated? From there, we can define invariants : properties that the system must preserve under the conditions established by its design. In the architecture discussed during the session, three dimensions were particularly important: Context → Logical isolation Identity → Cryptographic isolation Execution → Physical/process isolat
A Windows 11 VM in Proxmox VE was showing nearly 100% memory usage in monitoring. Inside Windows Task Manager, however, actual memory usage was only around 30–50% . At first glance, that looks like a monitoring problem. It wasn't. The issue was in the VM configuration: the PVE Ballooning Device had been disabled , which meant Proxmox VE was not receiving the guest memory statistics needed to reflect the actual Windows memory state. I encountered this while monitoring a Proxmox VE environment with OpsHome NOC. This post documents how I traced the discrepancy and fixed it. The symptom On the same Proxmox VE host, the memory usage of Ubuntu VMs looked normal. One Windows 11 VM was different. The VM had 24 GB of RAM configured, but the monitoring result remained close to: Memory: 100% Used: about 24.2 GB Total: 24 GB Inside Windows 11 Task Manager, however, the VM was clearly not using all of its memory. The difference looked roughly like this: Monitoring: 90%–100% Windows 11: 30%–50% That is too large a difference to treat as a normal sampling variation. If you encounter something similar, especially when Linux VMs on the same Proxmox host look normal, do not immediately assume: Windows has a memory leak The monitoring threshold is wrong The monitoring application is calculating memory incorrectly The more important question is: Is Proxmox VE actually receiving the correct memory statistics from the Windows guest? Checking BalloonService inside Windows 11 For Proxmox VE to obtain useful guest memory statistics from a Windows VM, the VirtIO Balloon driver and its related Windows service need to be available. Inside Windows 11, I opened PowerShell and checked BalloonService: Get-Service * balloon * The result showed: Running BalloonService So the Windows-side BalloonService was already installed and running. At this point, the guest-side service did not appear to be the problem. The next step was to check the VM configuration on the Proxmox side. Checking the Proxmox VE
Free Tokens Are Not an SLO: An Ops Cost Drill for AI Batch Queues This week, two numbers trended: a harness at 100%, a model at 30%. For platform teams, a better pair is queue age and deadline slack. This article is a cost drill for the simplest AI batch path: free tokens, free server, non-negotiable deadline. Disclosure: This article was prepared as part of MonkeyCode's product outreach. MonkeyCode offers free model access and a free server option. That capacity is real. It is not an SLO. The tokens cost nothing. The queue is patient. Your deadline is not. The missing variable Token cost is easy to measure. Operations cost is easy to ignore. A free endpoint converts a per-token bill into a per-hour bill. The bill becomes your time, your retries, and your queue age. This drill keeps the ledger honest. It answers one question: what does a completed request cost when the token price is zero? Topology # worker.py (minimal, single-threaded) import queue import time import csv work = queue . Queue () for i in range ( 1000 ): work . put ({ " id " : i , " prompt_tokens " : 512 , " max_tokens " : 256 }) def call_model ( payload ): # replace with your free model endpoint return { " ok " : True , " in_tokens " : 512 , " out_tokens " : 180 } completed = 0 retries = 0 started_at = time . time () while not work . empty (): item = work . get () attempt = 0 while attempt < 4 : try : call_model ( item ) completed += 1 break except Exception : retries += 1 attempt += 1 time . sleep ( 2 ** attempt ) The worker is deliberately single-threaded. Free capacity often serializes. Serialization turns a token problem into a time problem. Declared test conditions 1,000 requests. One worker process. One free model endpoint. No client-side rate limiting. Deadline: 30 minutes. Ledger: one CSV row per request. Ledger and report # cost_ledger.py import csv import time HOURLY_OPS_COST = 50.0 # loaded engineering rate, adjust def record ( item , elapsed , retries ): with open ( " ledger.csv " , " a
Introduction: The Systemic Failure in Application Security Onboarding Consider the scenario of a junior Application Security Engineer tasked with securing a 2-billion-line codebase, written in unfamiliar languages, within a one-month deadline. This is not a theoretical exercise but the lived experience of a recent graduate in India, whose public appeal for assistance reveals profound deficiencies in how organizations integrate and support junior AppSec talent. The pressure is unrelenting, the tools are insufficient, and the expectations are disconnected from practical realities. This case is not an isolated incident but a symptom of a broader organizational failure to address the complexities of application security in high-stakes environments. The engineer’s experience underscores a critical misalignment: the exponential growth in codebase complexity has outstripped the resources and guidance provided to those responsible for securing them. Absent a senior AppSec mentor, with limited proficiency in critical languages such as Laravel/PHP and C#, and equipped only with rudimentary tools like grep and Codex, the engineer is forced to navigate an environment rife with unseen risks. The consequences are twofold: individual inefficiency and self-doubt, compounded by organizational exposure to unmitigated security threats. The causal pathway is unambiguous: massive codebases + unrealistic deadlines + subpar tools + absent mentorship → overwhelmed engineers → cursory reviews → undetected vulnerabilities → systemic security compromise. The risks extend beyond individual burnout to include data breaches, financial liabilities, and reputational damage. This is not an edge case but a predictable outcome of organizational neglect. The urgency is undeniable. As software systems increase in complexity and cyber threats proliferate, the demand for competent, adequately supported AppSec professionals has never been more critical. Yet, organizations persist in failing to bridge the
The update turns product recommendations into a more direct revenue stream for creators, and for Amazon, the move puts its massive online marketplace inside one of the most popular video platforms.
Tech industry is perplexed by Trump’s plan to win AI race by taxing data centers.
Your coding agent talks to a model provider over HTTPS. That connection is a straight line: the agent asks, the provider answers, the answer lands in your editor. Nothing in the middle looks at what came back. For most of what an agent produces, that's fine. For the rest of it — the query built by string concatenation, the API key the model helpfully echoed back into a code sample, the eval() on user input — you find out later, in review, or in a scanner run, or never. This is a walkthrough of putting a policy layer in that line: a local proxy your agent points at instead of the provider, which inspects the response stream and decides allow , redact , or block before the text reaches you. I'll use Cencurity Engine because it's the one I build, it's Apache-2.0, and it runs entirely on your machine. The pattern generalises — if you're building your own gateway, the steps below are still the shape of the problem. What you need first Go installed (the engine is a Go binary you run from source) An API key for whatever provider your agent already uses An agent or IDE that lets you override the API base URL That last one is the real prerequisite. If your tool hardcodes the provider endpoint, none of this applies to it. Most don't: Roo Code, Continue, Claude Code and Gemini CLI all expose a base URL, and anything reading OPENAI_API_BASE will work too. Step 1: Start the gateway Clone the repo, open a terminal in it, and run: go run ./cmd/cast serve \ --listen :8080 \ --upstream https://api.openai.com \ --policy ./cast.rules.example.json Three flags, and each one is doing something you should understand before moving on: --listen is where the gateway accepts traffic. Local only. --upstream is your real provider base URL. Swap it for https://api.anthropic.com , https://api.deepseek.com , https://api.x.ai — whatever you actually use. --policy is the rule file. cast.rules.example.json ships in the repo and is a working starter set, not a placeholder. Note what is not in that com
I don't have an audience. No newsletter, no Twitter following, no YouTube channel. Every product I shipped before this one died the same way: a human had to discover it, and no humans knew I existed. So I flipped the buyer. An AI agent doesn't care about my follower count. It picks tools by spec, reliability, and price — from a registry it can search on its own. If I could ship a tool that agents discover, call, and pay for without a human in the loop, my distribution problem would stop mattering. That's what license-verify is: an Apify Actor that verifies a US contractor's license, surety bond, and insurance from official state data, exposed via the Model Context Protocol (MCP) so AI clients like Claude can call it mid-conversation, priced pay-per-event at $0.03 per successful lookup. Here's how I built it, the input-schema decisions that made it agent-callable, and the one-line billing bug that silently made every call free. Why contractor licenses I run a side business building tools for small contractor shops, so I knew the pain firsthand: before a homeowner (or a general contractor, or an insurance adjuster) hires a roofer, someone should check the license is active, the surety bond is real, and the insurance hasn't lapsed. In Washington State, all three live in the Department of Labor & Industries' open-data API on data.wa.gov. Most tools that "verify licenses" scrape an HTML page and return a status string. The official JSON gives you the actual bond amount and the insurance carrier. That's the difference between "probably fine" and "verified." It's also a perfect agent task: a small, well-defined question ("is ECOSTSC758NN licensed, bonded, insured?") with a structured answer an agent can act on. An AI assistant helping someone plan a renovation can reach for it mid-task, the same way it reaches for a calculator. The stack: one codebase, two doors The core is a TypeScript verification engine with a provider-per-state design. It ships through two doors: An Ap
Meta might be on the hook for $17.1 billion and a host of app changes under a new kids safety settlement, but it's already spinning the deal to its advantage. After years of being the national punching bag for social media harms, Meta has reached a settlement with 47 US states and several districts and […]
Adobe is rolling out an AI-heavy update for Photoshop that includes a new "optional" interface dedicated to its AI tools. Launching in beta, the "AI Assisted Editor" view will show all of Photoshop's AI features in a single toolbar, including its prompt-based image editor, background remover, an AI image extender, and more. There are also […]
You self-host S3-compatible storage on bare metal by installing a single Rust binary on a Linux server and pointing any S3 client at it. RustFS installs with one script, listens on port 9000 (S3 API) and 9001 (console), and is Apache 2.0 licensed. Single-node mode is production-ready today; multi-node clustering is still under testing. Every command below is copied verbatim from the official source cited beside it. This sandbox has no Docker daemon, so none of the commands were executed here; they are marked accordingly. Key Stats Fact Source RustFS installs with one command and runs as a systemd service on x86_64 or aarch64 Linux RustFS docs (Linux quick-start) Default S3 API port is 9000; console port is 9001 RustFS GitHub README Default credentials are rustfsadmin / rustfsadmin and must be changed RustFS README + docs RustFS is Apache 2.0 licensed and S3-compatible RustFS GitHub README Single-node mode is production-ready; distributed mode is still under testing RustFS README Feature & Status What is self-hosted S3-compatible storage? A self-hosted S3-compatible storage server is a program you run on your own hardware that speaks the Amazon S3 API. Applications using AWS SDKs, the aws CLI, or MinIO's mc can talk to it without code changes, because the bucket, object, and credential model matches S3. The difference from a cloud bucket is ownership: the disks, the network path, and the uptime are yours. RustFS is one such server, written in Rust and licensed under Apache 2.0. It exposes the S3 API on port 9000 and a web console on 9001, and it stores objects on the local filesystem. Because it is S3-compatible, the same client code that targets AWS S3 also targets a RustFS node. That compatibility is the whole point of self-hosting here: you get an S3 endpoint without renting one. Why run object storage on bare metal? Running object storage on bare metal means installing the server directly on a Linux machine instead of in a container or a managed cloud. The appeal
Linux server running out of memory? Learn how to diagnose and fix high memory usage with real commands — before it takes down your app. Your app starts slowing down, the OOM killer fires, or your monitoring page turns red — and the culprit is memory. High memory usage on a Linux server is one of the most common production crises for small teams, and it's easy to misread. Linux intentionally uses most of your RAM for caching, so a server showing 95% memory used isn't necessarily in trouble. But one that's exhausting real working memory and swapping is. Here's how to tell the difference and actually fix it. Step 1: Get a Clear Picture of What's Using Memory Start with the basics. Run 'free -h' to see total, used, free, and available memory. Focus on the 'available' column — that's the real number. It accounts for reclaimable cache and is far more useful than 'free'. free -h — quick overview of RAM and swap usage vmstat 1 5 — five one-second snapshots; watch the 'si' and 'so' columns for swap-in and swap-out activity cat /proc/meminfo — full breakdown including Slab, PageTables, and AnonPages If swap is actively being used (si/so values above zero consistently), your server is genuinely memory-constrained. That's different from swap space existing but sitting idle. Step 2: Find the Processes Eating Your RAM Once you know memory is tight, you need to know what's consuming it. Run 'ps aux --sort=-%mem | head -20' to list the top 20 processes by memory percentage. For more detail on actual RSS (resident set size) in human-readable form: ps -eo pid,ppid,cmd,%mem,rss --sort=-%mem | head -20 RSS is the memory a process actually holds in RAM — not virtual memory, which is often misleadingly large. Another useful tool is 'smem', which calculates PSS (proportional set size) and gives a fairer view when processes share memory libraries. Install it with 'apt install smem' or 'yum install smem', then run 'smem -r -k | head -20'. Look for processes with unexpectedly high RSS. A Nod
Most LlamaIndex setups end up with two separate backends once you go beyond plain vector search: a vector store for VectorStoreIndex , and a separate graph database for PropertyGraphIndex when you need relationship-aware retrieval (GraphRAG). Two services, two connection strings, two things to keep in sync. This is a walkthrough of backing both index types with SynapCores instead — one engine, one connection, both index types. Setup docker run -d --name synapcores -p 8080:8080 \ -e AIDB_ACCEPT_LICENSE = 1 \ -v synapcores-data:/var/lib/synapcores \ ghcr.io/synapcores/community:latest pip install llama-index llama-index-vector-stores-synapcores llama-index-graph-stores-synapcores Both integration packages are independently published on PyPI: llama-index-vector-stores-synapcores llama-index-graph-stores-synapcores Vector store — standard RAG from llama_index.core import VectorStoreIndex , StorageContext , Document from llama_index.vector_stores.synapcores import SynapCoresVectorStore vector_store = SynapCoresVectorStore ( uri = " http://localhost:8080 " , embedding_dim = 1536 ) storage_context = StorageContext . from_defaults ( vector_store = vector_store ) docs = [ Document ( text = " SynapCores runs vector search, graph traversal, and SQL in one engine. " )] index = VectorStoreIndex . from_documents ( docs , storage_context = storage_context ) query_engine = index . as_query_engine () response = query_engine . query ( " What does SynapCores combine into one engine? " ) print ( response ) The vector store implements the full BasePydanticVectorStore ABC — add , delete , query , delete_nodes , clear , plus the async surface. Metadata filtering supports the full MetadataFilters grammar: all 12 operators ( EQ , NE , GT / GTE / LT / LTE , IN , NIN , TEXT_MATCH , TEXT_MATCH_INSENSITIVE , CONTAINS , IS_EMPTY ) with AND / OR / NOT and nested groups — so you're not giving up filtering power by moving off a dedicated vector DB. If you already have data in SynapCores from a prev
The electric Torcal will be Bentley's entry model and cost less than a Bentayga.
A 30-character bio limit that cuts off mid-emoji isn't a rendering bug — it's .length counting UTF-16 code units instead of what's on screen. Intl.Segmenter counts graphemes, words, and sentences the way a reader actually sees them, and every major browser supports it now.
TL;DR We're building a caption evaluation harness that scores a WebVTT file on four axes instead of one: word error rate under a fixed normalizer, missed entity rate on domain terms, median cue timing offset, and reading rate in characters per second. Python 3.12, jiwer , whisper_normalizer , webvtt-py . Run it on every model or vendor change. A caption file can score 96% accurate and still be unusable. WER counts substitutions, insertions and deletions and weighs each one the same, so "fifteen milligrams" becoming "fifty milligrams" costs exactly as much as "the" becoming "a". It also throws away every timestamp before it starts, which means synchronization and readability are invisible to it. Let's measure the other three things. 0. Setup 🛠️ python3 -m venv .venv && source .venv/bin/activate pip install jiwer whisper_normalizer webvtt-py $ pip list | grep -Ei 'jiwer|whisper|webvtt' jiwer <your version> webvtt-py <your version> whisper-normalizer <your version> Pin whatever you install, and pin it in CI. The APIs below move between majors, which is exactly why the next tip exists. 💡 Tip: jiwer.compute_measures() is gone in recent versions. It is jiwer.process_words() now, and it returns a WordOutput dataclass. Most blog posts you will find still use the old name. 1. Parse the VTT into text plus timings # captions.py from dataclasses import dataclass import webvtt @dataclass class Cue : start : float end : float text : str @property def duration ( self ) -> float : return self . end - self . start @property def lines ( self ) -> list [ str ]: return self . text . split ( " \n " ) @property def flat ( self ) -> str : return " " . join ( l . strip () for l in self . lines ) @property def chars_per_second ( self ) -> float : return len ( self . flat ) / self . duration if self . duration > 0 else float ( " inf " ) def _to_seconds ( ts : str ) -> float : h , m , s = ts . split ( " : " ) return int ( h ) * 3600 + int ( m ) * 60 + float ( s ) def load_vtt ( path : str ) -
TL;DR -c copy can only cut on keyframes, so your 12.4s trim starts wherever the last keyframe was. We'll build a smart-trim script that probes keyframe positions with ffprobe , re-encodes only the head and tail fragments, stream copies everything between them, and concatenates the three. Frame accurate output, encoding cost proportional to two GOPs instead of the whole file. Tested with FFmpeg 9.0 "Lei" (released 2026-08-04) and Node 22.x. The JS is ESM, so put "type": "module" in your package.json before running any of it. Everything here also works on FFmpeg 7.x and 8.x; nothing we use is new. The problem, in two commands 🎬 # fast, and wrong ffmpeg -ss 12.4 -i input.mp4 -t 20 -c copy fast.mp4 ffprobe -v error -show_entries format = start_time,duration -of default = nw = 1 fast.mp4 # start_time=0.000000 # duration=20.388000 <- we asked for 20, starting at 12.4 The clip is long by the distance from our requested start back to the previous keyframe, and every frame in it is shifted earlier than the user asked for. Stream copy moves compressed packets without decoding them. Most frames in a compressed stream only describe the difference from their neighbors, so the only place you can start is a keyframe. FFmpeg snaps back to the nearest preceding one, and your clip starts early. # accurate, and slow on a long source ffmpeg -ss 12.4 -i input.mp4 -t 20 -c :v libx264 -crf 20 -c :a aac slow.mp4 We want the accuracy of the second and roughly the cost of the first. 1. Look at your keyframes first Before writing any code, find out how bad the problem is for your content: ffprobe -v error -select_streams v:0 \ -show_entries packet = pts_time,flags \ -of csv = print_section = 0 input.mp4 | grep 'K' | head -20 0.000000,K__ 2.002000,K__ 4.004000,K__ 6.006000,K__ Two second GOPs here, so worst-case error is about two seconds. Screen recorders and some camera output emit keyframes on scene change only, and there the gaps can be 30 seconds or more. That distribution is the real spe
NLP stopped being a data science specialty about two years ago. It's backend infrastructure now. If you're building APIs that process user input, handle search, manage support tickets, parse documents, or power any feature where humans communicate with your system in natural language, you're doing NLP whether you call it that or not. The difference between a backend developer who understands NLP techniques and one who doesn't is the difference between building a search endpoint that actually finds what users want and building one that matches keywords and returns garbage for anything slightly ambiguous. This is the reference guide we wish we'd had when we started integrating NLP into production backend services. Fifteen techniques, each with a runnable code snippet, ordered from the most immediately useful to the most architecturally advanced. Every example runs in Python. Install the dependencies as needed, we'll note them for each technique. 1. Text tokenization The atomic operation. Everything else depends on splitting text into meaningful units. import spacy nlp = spacy . load ( " en_core_web_sm " ) text = " Dr. Smith ' s appointment at 3:30pm was rescheduled. " doc = nlp ( text ) tokens = [ token . text for token in doc ] # ['Dr.', 'Smith', "'s", 'appointment', 'at', '3:30pm', 'was', 'rescheduled', '.'] SpaCy handles the edge cases that naive split-on-whitespace misses, abbreviations, contractions, timestamps. If your backend processes any user-generated text, tokenization is step zero. 2. Named entity recognition (NER) Extracting structured data from unstructured text. Names, dates, amounts, locations, the things your database actually needs. doc = nlp ( " Send $5,000 to Acme Corp in Singapore by March 15th " ) for ent in doc . ents : print ( f " { ent . text : 20 } { ent . label_ } " ) # $5,000 MONEY # Acme Corp ORG # Singapore GPE # March 15th DATE We use NER on every inbound support ticket to auto-tag customer, product, and amount entities before the ticket