Introduction When a query runs in ClickHouse®, the database does much more than simply read data and return results. Before execution begins, ClickHouse® parses the SQL statement, analyzes it, applies optimizations, and builds an execution plan that determines the most efficient way to process the query. Understanding query execution plans is one of the most valuable skills for anyone working with ClickHouse®. They provide visibility into how queries are executed, helping you identify bottlenecks, validate optimization efforts, and troubleshoot performance issues. In this article, we'll explore how ClickHouse® generates execution plans, the different EXPLAIN modes, and how to interpret them for better query optimization. Why Query Execution Plans Matter A SQL query defines what data you want, but it doesn't explain how the database retrieves it. Consider the following query: SELECT country , count () FROM events GROUP BY country ; Although the query looks simple, ClickHouse® must determine: Which data parts to read Whether primary indexes can reduce the scan If data skipping indexes can be used How aggregation should be performed Whether parallel execution is possible How intermediate results should be merged A query execution plan provides answers to these questions, making it an essential tool for performance tuning. The ClickHouse Query Lifecycle Every query passes through several stages before producing results. The lifecycle typically looks like this: SQL Query │ ▼ Parser │ ▼ Analyzer │ ▼ Optimizer │ ▼ Query Plan │ ▼ Execution Pipeline │ ▼ Results Each stage plays an important role: Parser validates SQL syntax. Analyzer resolves tables, columns, and expressions. Optimizer applies query optimizations. Query Plan determines the logical execution steps. Pipeline distributes work across multiple threads. Execution processes the data and returns the results. Understanding this workflow makes execution plans much easier to interpret. Introducing the EXPLAIN Statement

TL;DR: A single eval number hides its own uncertainty. Eval confidence intervals from bootstrap resampling turn a point estimate like 84.2% accuracy into a range, so you stop shipping models on a difference that is noise. Two checkpoints came back from a fine-tuning run at 84.2% and 85.7% on our 500-example agent eval set. The 1.5 point gap read like a win, and someone wanted to promote the second checkpoint to staging. Before that, I wanted eval confidence intervals on both numbers, because a 500-example set carries more sampling error than most teams admit. At 500 examples, the 95% interval on a single accuracy near 85% spans roughly 3 points on each side. The win sat well inside the noise. I lead the fine-tuning and evaluation team at Nexus Labs, and the most common mistake I see is treating an eval score as exact. It isn't. Your eval set is a sample drawn from the input space you care about, and a different 500 examples would return a different number. Confidence intervals make that variance visible. What an eval confidence interval actually tells you An eval confidence interval is a range around a metric, like accuracy or F1, that quantifies how much the score would move if you resampled the eval set. A 95% bootstrap interval of [81.0%, 87.1%] means that across thousands of resamples of your data, 95% of the recomputed scores fell in that band. It measures sampling noise, not model quality. That distinction matters. Two checkpoints scoring 84.2% and 85.7% with overlapping intervals are, as far as your eval set can tell, indistinguishable. Card et al. showed in "With Little Power Comes Great Responsibility" that many NLP experiments are underpowered to detect the effect sizes they report. Computing bootstrap confidence intervals The bootstrap is resampling with replacement. You take your per-example results, draw N of them with replacement many times, recompute the metric each time, and read percentiles off the resulting distribution. There's no assumption that

Introduction This is the second part of sharing my journey to create a microservices-based backend system, in the previous part, I introduced the system and its services. In this part I am going to mention the main things that happened with me from then until now. Transitioning to online DBaaS platforms The first main thing was to transition my databases from my local device to accessible over the internet. I used Neon and MongoDB Atlas . Although performance-wise it is better to deploy the database on the same server that the whole system so all services can access the databases without network overhead , This solution is better from a point, that is avoiding consuming the free VM instance that I got to host my main services, as with DBaaS platforms I will not require storage for databases or additional overhead to handle the DBMS on a free small resources-constrained VM. Observability Observability is one of the main concerns in any system, it gives the ability for the system to expose what happens inside it without any need to guess and manually trace the code to determine where the error may happened. I utilized OpenTelemetry , as I found it is most used and accepted tool to log, trace and collect metrics about the system and the traffic. Also, I loved that it is not related to specific framework, that is .NET by the way, I loved the idea that it is standalone tool. But logging and tracing and metrics collection will not be beneficial if we do not see it actually and can achieve monitoring from those telemetry data, so I used Grafana Cloud to export the telemetry data to some place that is accessible online and a tool that can generate dashboards and visualizing for the metrics ( Prometheus ), and UI that can show all the telemetry data easily. Deployment Until this point, we have a system that is fully functional and have consistent docker configuration for its services via Docker Compose, and it database is already there and available. Now this is the point at

TechCrunch's StrictlyVC evening in Los Angeles late last week brought together two of the more straight-talking investors working in AI right now. They were as entertaining as they were illuminating.

I applied to a YC W25 startup the normal way. Filled out the form, wrote a decent cover letter, hit submit. Silence. While waiting, I found their open-source repo on GitHub. Read through the codebase out of genuine curiosity I wanted to understand what they were actually building. Found a bug. Fixed it. Opened a PR. It got merged in 2 days. They still hadn't replied to my application. Here's what that taught me about job hunting in 2025: A cover letter tells someone what you claim you can do. A merged PR shows them. One of those gets read. The other gets filed under "maybe later" -which is just "no" with extra steps. I'm not saying cold applications are dead. I'm saying they're the last resort, not the first move. If a company has a public repo, you have a backdoor that most applicants don't even think to try. Read the code deep and find something small but real. Fix it and Open a PR. Now you're not a stranger in their inbox you're someone who already ships for them. The reply came eventually, by the way. But by then, the maintainers already knew my GitHub handle. That matters more than you think. Have you ever landed something through a contribution instead of an application? Drop it in the comments curious how many people have done this.

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Here's a thinking process: Analyze User Input: Role: Ghostwriter for Roberto Luna Osorio Editorial Profile: Developer Storytelling (primary), Build in Public, Técnico, Reflexivo. Philosophy: Share the process/learnings, not just the perfect result. Mandatory narrative questions: Problem, First attempt, What went wrong, How solved, What learned, What's next. Tone: First person, direct, honest, technical but accessible, curious. Avoid corporate jargon, clickbait, marketing hype, false modesty, empty summaries. Language: Spanish (natural/colloquial tech MX/LatAm) OR English (conversational, dev-friendly). Wait, the prompt says "English only (Dev.to is primarily English)" for this specific article. I'll stick to English as instructed for the Dev.to angle. Angle: TECHNICAL DEEP-DIVE ("HOW I BUILT IT"). Focus on code, architecture, specific files. Different from Medium's narrative style. Style: Technical, precise, code-forward. Real file/function names, error messages. First person but engineer-voice. English only. Mandatory Structure: TL;DR, The Problem, What I Tried First, The Implementation, Key Takeaway, What's Next. Length: 800-1200 words. Tags: #vibecoding #buildinpublic + relevant tech tags. Input Data: Repo: VS, Date: 2026-06-23. Commits show v1.6.0 sprint 1, booking reminders, /confirm/:token, notifications, bulk actions, pipeline v2. Files modified: booking-reminders.service.ts , booking.controller.ts , email.cron.ts , notifications.controller.ts , NotificationBell.tsx , confirm/[token]/page.tsx , ventas/pipeline/page.tsx , etc. Diffs show version bumps, cron integration, notification controller refactor, new components. Constraint: Do NOT repeat angles from this week: "El control de acceso y la caja negra de las publicaciones". Choose a completely different angle. Final Instruction: Write complete article. Start directly with TL;DR. Include actual code snippets. Do NOT write a story — write a technical breakdown. Map to Editorial Profile & Constraints: Profile

Introduction Every serious backend developer eventually faces the same problem: you need to make multiple changes to a database as part of a single business operation, and you need all of them to succeed or none of them to go through. Partial updates are worse than no updates at all - they leave your data in an inconsistent state that can be nearly impossible to debug in production. This is not a new problem. Enterprise developers have been solving it for decades, and Martin Fowler documented the canonical solution in his 2002 book Patterns of Enterprise Application Architecture : the Unit of Work pattern. In this article we are going to go deep on what Unit of Work is, why it exists, how it works internally, and how to build a clean, production-quality implementation from scratch in Python using only the standard library. By the end you will have a working implementation you can adapt to any project, and a solid understanding of how popular frameworks like SQLAlchemy and Django ORM implement this pattern under the hood. The full source code is available on GitHub: 👉 github.com/diegocastillo12/unit-of-work-python - ## Background: What is the Unit of Work Pattern? The Unit of Work pattern is part of Martin Fowler's catalog of Patterns of Enterprise Application Architecture (PoEAA), a collection of battle-tested solutions for common problems in enterprise software design. Fowler defines it as follows: > "A Unit of Work maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems." Let's unpack that definition carefully. "Maintains a list of objects affected by a business transaction" - this means the Unit of Work acts as a tracker. When your business logic creates a new object, modifies an existing one, or marks one for deletion, it does not immediately write to the database. Instead, it registers the change with the Unit of Work, which keeps an in-memory list of everything that ne

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One of the main challenges related to web development is maintaining state across the client and the server and most web applications have to solve this somehow. Because of this reason, so-called sync engines have become available as they can own a large part of data synchronization. In his MSc thesis, my student Mikael Siidorow looked into the space to find out the limits of generalized sync. He did his study through multiple methods including literature review, interviews, and a case study. In

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The biodegradable material can help improve healing after surgery—or an avocado-related accident.

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