GreatReads - Blog Aggregator · Phoenix Framework

AI

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Lalit Maganti 2 weeks ago

On "When impressive performance gains do not matter"

When impressive performance gains do not matter is a very nice article covering some ways in which going after performance alone is not sufficient without considering the wider picture. It resonated a lot with how I think about performance. If there are multiple bottlenecks in the pipeline—and with these systems, this is common—the overall throughput will not improve until every last bottleneck is removed. His focus is on distributed systems bottlenecks, but I’ve hit the same “do-nothing” speedups when optimizing client side programs. Usually this comes from spending a lot of time thinking something was the bottleneck when it wasn’t. CPU profiling is where this bites me most: it tells me “function X is taking 30% of the cycles” and I think “oooo, there’s a lot of gains to be made there”. I build a microbenchmark for X, optimize it and there’s only a marginal gain at the high level. While disappointing, I’ve become used to it over time and internalized that performance is highly non-linear and actually knowing where the problem lies is really hard.

DevOps

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Lalit Maganti 4 weeks ago

syntaqlite 0.6: SQLite dot commands and pyodide

Since my original launch post for syntaqlite, I’ve been quietly working away on it in the background. A lot of the work has been fixing correctness bugs which I discovered as I integrated it into production as the parser for PerfettoSQL in the Perfetto trace processor: as I wrote previously, this has been my dream for over 8 years so it’s amazing to see it finally realized. Just today, I released syntaqlite 0.6 , the most interesting release since the original launch, so I wanted to talk about what’s new. The biggest step forward for real world applicability is that we now support SQLite dot commands : SQLite scripts are very common in the wild and in the past we would simply error on dot commands like and , causing spurious warnings and an inability to format files like this properly. Now, these lines will be silently ignored while still parsing, formatting and validating the SQL inside!

Sql

Open Source

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Lalit Maganti 1 months ago

TIL: Iroh: peer-to-peer networking for app developers

I came across Iroh ( via , via ) today as it hit 1.0 and found it a really interesting solution to a problem I knew existed but had not thought a lot about. Judging from the comment sections, it seems pretty clear that lots of people are confused as to exactly what Iroh is. I don’t think their launch post does their product justice at all, and their tagline is “IP addresses break, dial keys instead” which sounds cool, but if you think about it for just a second, you’ll end up with lots of questions. The biggest one is: “so how is this different from a mesh VPN like Tailscale, ZeroTier, Netbird, etc.?” It’s only after reading a lot of developers’ comments on the threads that I feel I understand: Iroh is aimed at application developers who want to communicate P2P between machines running their app, while mesh networks are aimed at network admins who want to connect devices they own/manage together.

DevOps

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Lalit Maganti 1 months ago

17 bugs in 10 weeks from AI security scanning

Over the last several weeks, I’ve been receiving more security bug reports for Perfetto’s trace processor than I ever have before, all of them found by AI. And I’m very happy about it! These are bugs that would almost certainly not have been found a year ago and it feels good to close these loopholes even though trace processor is by no means security critical. For years, security researchers concentrated their time on the highest-stakes targets: kernels, cryptography libraries, password managers. But there’s a lot of code out there which is security-relevant but not truly security-critical. In my experience, these sorts of projects didn’t draw much attention. Now systems in the long tail can get that attention which they wouldn’t have before. Trace processor is a project which sits squarely in that long tail. It’s a C++ library (yes, Rust would be the obvious choice today but it’s not practical to rewrite, see footnote 1 ) for processing recorded traces of various formats. These are typically traces you collected yourself or in your test infra and process offline so “untrusted input” isn’t much of a concern.

AI

Security

C++

Rust

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Lalit Maganti 2 months ago

Which country voted the best at Eurovision?

Eurovision was on yesterday. I’ve never been interested much in the musical side but the weird political dynamics of Eurovision voting have always fascinated me; I tune in each year just for them and somewhat snarky commentary of Graham Norton, the UK commentator. As I was watching the jury votes come in, a question popped into my head: Which country has voted the best in Eurovision? That is, which country was best at picking the eventual top 10 and in the right order? Strangely enough, while there’s plenty of work on voting blocs and bilateral biases at Eurovision, most of it asks who votes for whom ; I wanted to ask who votes accurately . I couldn’t find anyone asking the question that way, so I decided to do some data analysis myself. To begin to answer this question, I first needed to formalize what “best” even means. That is, some mathematical notion of “good” and “bad”.

Data Analysis

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Lalit Maganti 2 months ago

Don't answer the first question

In my work on Perfetto, a performance debugging tool, one question I get often is: “how do I split a Perfetto trace into multiple files?” Instead of answering directly, I say: “there isn’t an easy way to do that, but what’s leading you to collect traces large enough to want to split?” This is one of my golden rules at work. When a user asks me something “weird”: don’t answer the first version of the question . On the surface this might appear like I’m talking about the XY problem , but that stops one step short. It treats the user’s stated question as a puzzle to decode: figure out what they really meant, answer that, move on. I think we can go much further. Instead, the confusion that produced the wrong question is itself an opening, and the conversation it sparks is valuable to both sides. The user walks away with a better mental model of the tool. I walk away with a clearer picture of where the product confuses people. And sometimes, between us, we figure out that the product itself needs to change.

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Lalit Maganti 3 months ago

Eight years of wanting, three months of building with AI

For eight years, I’ve wanted a high-quality set of devtools for working with SQLite. Given how important SQLite is to the industry 1 , I’ve long been puzzled that no one has invested in building a really good developer experience for it 2 . A couple of weeks ago, after ~250 hours of effort over three months 3 on evenings, weekends, and vacation days, I finally released syntaqlite ( GitHub ), fulfilling this long-held wish. And I believe the main reason this happened was because of AI coding agents 4 . Of course, there’s no shortage of posts claiming that AI one-shot their project or pushing back and declaring that AI is all slop. I’m going to take a very different approach and, instead, systematically break down my experience building syntaqlite with AI, both where it helped and where it was detrimental. I’ll do this while contextualizing the project and my background so you can independently assess how generalizable this experience was. And whenever I make a claim, I’ll try to back it up with evidence from my project journal, coding transcripts, or commit history 5 .

AI

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Lalit Maganti 4 months ago

syntaqlite: high-fidelity devtools that SQLite deserves

Most SQL tools treat SQLite as a “flavor” of a generic SQL parser. They approximate the language, which means they break on SQLite-exclusive features like virtual tables , miss syntax like UPSERT , and ignore the 22 compile-time flags that change the syntax SQLite accepts. So I built syntaqlite : an open-source parser, formatter, validator, and LSP built directly on SQLite’s own Lemon-generated grammar. It sees SQL exactly how SQLite sees it, no matter which version of SQLite you’re using or which feature flags you compiled with. It ships as a CLI , VS Code extension , Claude Code LSP plugin , and C / Rust libraries. There’s also a web playground which you can try now: paste any SQLite SQL and see parsing, formatting, and validation live in the browser, no install needed. Full documentation is available here . Here’s syntaqlite in action: Formatting with the CLI Validation with the CLI

Rust

Sql

Open Source

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Lalit Maganti 5 months ago

Rendering 100k trace events faster with exponential search

We’ve recently been looking into optimizing rendering performance of the Perfetto UI on large traces. We discovered that there was some inefficiency in our data fetching logic, especially when you’re very zoomed out. In this case, there can be a lot of slices (spans) which are so small that they take less than one pixel of width. So for each pixel, we need to figure out “what is the event which we should draw for this pixel”. Over time we’ve come to the conclusion that the best thing to draw is the slice with the largest duration in that pixel. We can break this into two sub-problems: We’re going to focus on 1) in this post as that’s where the slowdown was. 2) is fascinating but also surprisingly orthogonal. If you’re interested, I would suggest reading this excellent post from Tristan Hume explaining the basic algorithm we use. What is the range of events which correspond to each pixel? What is the event with the maximum duration for that pixel?

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Lalit Maganti 5 months ago

The surprising attention on sprites, exe.dev, and shellbox

Over the last few weeks, three new products have announced themselves on Hacker News to great success, each making the frontpage: All three have a very simple pitch: they will give you full access to Linux virtual machines to act as a sandboxed developer environment in the cloud. At first glance, the attention these have gotten is very head-scratching. The idea of a Linux VPS has been around for more than 20 years at this point and VPS providers like DigitalOcean and Hetzner are widely known and used in the industry. From a technological standpoint, there’s very little revolutionary here. Is it price then? Well no: the hardware specs are pretty awful for what you pay. For example, exe.dev gives you 2 CPUs and 8GB RAM shared across your whole account for $20/month. For comparison, at Hetzner for roughly that price, you can get a single VPS with 16 CPUs and 32GB RAM… Sprites (fly.io) with 508 votes and hit #7 exe.dev with 457 votes and hit #2 shellbox.dev with 316 votes and hit #4

DevOps

Cloud

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Lalit Maganti 6 months ago

Why Senior Engineers Let Bad Projects Fail

When I was a junior engineer, my manager would occasionally confide his frustrations to me in our weekly 1:1s. He would point out a project another team was working on and say, “I don’t believe that project will go anywhere, they’re solving the wrong problem.” I used to wonder, “But you are very senior, why don’t you just go and speak to them about your concerns?” It felt like a waste of his influence to not say anything. So it’s quite ironic that I found myself last week explaining to a mentee why I thought a sister team’s project would have to pivot because they’d made a poor early design choice. And he rightfully asked me the same question I had years ago: “why don’t you just tell them your opinion?” It’s been on my mind ever since because I realized I’d changed my stance on it a lot over the years.

Business

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Lalit Maganti 6 months ago

One Number I Trust: Plain-Text Accounting for a Multi-Currency Household

Two people. Eighteen accounts spanning checking, savings, credit cards, investments. Three currencies. Twenty minutes of work every week. One net worth number I actually trust. The payoff: A single, trustworthy net worth number growing over time. No app did exactly what I needed, so I built my own personal finance system using plain-text accounting principles and a powerful Python library called Beancount . This post shows you how I handle imports, investments, multi-currency, and a two-person view. It all started during the 2021 tax season. I had blocked out an entire weekend and was juggling statements, trying to compute capital gains, stressing about getting the numbers mixed up. “This is chaos”, I thought. “There must be a way to simplify this with automation”. Being a software engineer, I did what felt natural and hacked together a bunch of scripts on top of a database.

Tutorial

Python Finance

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Lalit Maganti 7 months ago

Homepage Redesign, Light Mode and More

Just a quick note documenting some recent changes to the blog. Nothing groundbreaking, but enough accumulated updates that I wanted to write them down. The homepage used to be a chronological list of articles; your classic default blog format. I’ve redesigned it into more of a two-pane “dashboard” feel. The reason? My content is quite varied: I have long essays and technical write-ups but also short TIL or notes posts (like this one!). Having a way to differentiate between them while also scanning across the titles of different types of posts felt really valuable. I was inspired by this post which I stumbled across. A couple of days ago, a reader emailed me and asked if I could add a light mode to the blog because they were reading in a bright environment. Though personally I prefer dark mode, I appreciate not everyone agrees so it made sense to add.

Web Development

Design

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Lalit Maganti 7 months ago

Why I Ignore The Spotlight as a Staff Engineer

Discussed on Hacker News , lobste.rs and r/programming. Lately I’ve been reading Sean Goedecke’s essays on being a Staff+ engineer. His work (particularly Software engineering under the spotlight and It’s Not Your Codebase ) is razor-sharp and feels painfully familiar to anyone in Big Tech. On paper, I fit the mold he describes: I’m a Senior Staff engineer at Google. Yet, reading his work left me with a lingering sense of unease. At first, I dismissed this as cynicism. After reflecting, however, I realized the problem wasn’t Sean’s writing but my reading. Sean isn’t being bleak; he is accurately describing how to deal with a world where engineers are fungible assets and priorities shift quarterly. But my job looks nothing like that and I know deep down that if I tried to operate in that environment or in the way he described I’d burn out within months . Instead I’ve followed an alternate path, one that optimizes for systems over spotlights , and stewardship over fungibility .

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Lalit Maganti 7 months ago

We stopped roadmap work for a week and fixed 189 bugs

Discussed on Hacker News , lobste.rs and r/programming It’s Friday at 4pm. I’ve just closed my 12th bug of the week. My brain is completely fried. And I’m staring at the bug leaderboard, genuinely sad that Monday means going back to regular work. Which is weird because I love regular work. But fixit weeks have a special place in my heart. Once a quarter or so, my org with ~45 software engineers stops all regular work for a week. That means no roadmap work, no design work, no meetings or standups. Instead, we fix the small things that have been annoying us and our users: The rules are simple: 1) no bug should take over 2 days and 2) all work should focus on either small end-user bugs/features or developer productivity. an error message that’s been unclear for two years a weird glitch when the user scrolls and zooms at the same time a test which runs slower than it should, slowing down CI for everyone

Testing

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Lalit Maganti 8 months ago

TIL: Number in man page titles (e.g. sleep(3))

If you do Linux systems programming, you will have likely pored over pages, either on the command line or, my personal preference, using the excellent man7.org or linux.die.net . I’ve always seen the numbers in and and idly wondered what they meant, but never actually bothered to look them up. That is, until a review comment on a pull request: reviewer: nit: it’s not a syscall, so “man 2” is incorrect So I looked it up. The answer was in the page (also accessible via the delightful command): The table below shows the section numbers of the manual followed by the types of pages they contain. So my colleague was right and the code should have read as is a libc library call.

C#

Linux

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Lalit Maganti 8 months ago

When Good Technical Writing Isn't Enough

Last week, I came across Don’t Build an Audience . It’s a fascinating post and has been occupying a lot of my “free thinking” time. I strongly suggest reading it as it’s well written and excellently argued. To summarise what it tries to say: I’m a very strong believer in the core message of “make cool things rather than chase followers”. It’s something I’ve done throughout my life and I have zero interest in changing that going forward. But I don’t agree with the argument that the market is efficient for all types of written content. I think the author is over-indexing on what they write about: topics accessible for a wide audience and do not require background knowledge (e.g. philosophical musings, economic theory, social dynamics). I write about technical topics . Sometimes this can be so deeply in the weeds that at most a few thousand people in the world would care about it. But it might totally change how these people work: it might teach about how to debug performance in their code, let them know about a new approach to analysing data or even inspires them build an entirely new program. The market for written content on the web (blog posts, articles etc) is “efficient”: in other words, great work will find its audience without you needing to build a “following” first. “Liquidity providers” (influencers, curators, algorithms) are incentivized to share good content because it benefits them. They maintain credibility and engagement by surfacing quality work. Specifically called out are Substack, Alexey Guzey and Tyler Cowen. You can speed up “distribution” of what you write with minimal effort. Just 30 minutes to email a few key people and posts on the “right” platforms. Therefore, focus on creating excellent work rather than “building an audience”. If it’s truly good, the market will ensure it reaches “everyone who matters”.

Writing

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Lalit Maganti 8 months ago

CAST(x AS STRING) casts to integer in SQLite

Discussed on lobste.rs . As an “SQLite consultant” for my local area of Google, I often have people come to me having written SQL like: and ask me “Why is baz always an integer?! Have I hit an SQLite bug?”. I have to again reach for my list of “odd quirks that SQLite has that people don’t know about”. Because this is not a bug, at least according to the SQLite manual. Instead, the correct way to write the above query is: The reason for this? Quoting from “Determination of Column Affinity” For tables not declared as STRICT, the affinity of a column is determined by the declared type of the column, according to the following rules in the order shown: Otherwise, the affinity is NUMERIC. does not match any of the numbered rules and so fallback to affinity which, in the general case, means integer. Due to SQLite’s staunch stance of being “backwards compatible” there’s very little chance of this paper-cut ever going away. But at least next time someone comes to me with this issue, I’ll be able to link to this post instead of writing the same thing for the nth time :) If the declared type contains the string “INT” then it is assigned INTEGER affinity. If the declared type of the column contains any of the strings “CHAR”, “CLOB”, or “TEXT” then that column has TEXT affinity. Notice that the type VARCHAR contains the string “CHAR” and is thus assigned TEXT affinity. If the declared type for a column contains the string “BLOB” or if no type is specified then the column has affinity BLOB. If the declared type for a column contains any of the strings “REAL”, “FLOA”, or “DOUB” then the column has REAL affinity.