ContentPosts from @varbear..
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@varbear shared a link, 2 weeks, 5 days ago
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How We Reduced Median Memory Estimation Error by 99%, With the Help of AI

The compaction pipeline at Mixpanel ran into memory estimation issues causing OOMKills. By implementing AI-assisted analysis, they were able to reduce median estimation errorby 99%, leading to a significant improvement in memory estimation accuracy. Through thorough analysis and exploration of alter.. read more  

How We Reduced Median Memory Estimation Error by 99%, With the Help of AI
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@varbear shared a link, 2 weeks, 5 days ago
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A Couple Million Lines of Haskell: Production Engineering at Mercury

Mercury runs ~2M lines ofHaskellin production. They choseTemporalto replace cron and DB-backed state machines. Durable workflows replace brittle coordination. They open-sourced aHaskellSDK forTemporal, wired inOpenTelemetryhooks, and pushed records-of-functions plus domain-error types... read more  

A Couple Million Lines of Haskell: Production Engineering at Mercury
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@varbear shared a link, 2 weeks, 5 days ago
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When upserts don't update but still write: Debugging Postgres performance at scale

The Datadog team introduced a new upsert query to track inactive hosts, but it unexpectedly increased disk writes and WAL syncs due to row locking. By digging into Postgres's Write-Ahead Logging (WAL) and rewriting the query using a Common Table Expression (CTE), they avoided unnecessary overhead an.. read more  

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@varbear shared a link, 2 weeks, 5 days ago
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How To Make a Fast Dynamic Language Interpreter

Zef's AST-walking interpreter posts a 16.6× speed-up. The gains come from surgical changes:64-bit tagged values,AST node & RMW specialization,symbol hash-consing,inline caches, and a shapedobject model. Developers built it onFil-C++and later ported it toYolo-C++. The Yolo build adds ~4x speed, at th.. read more  

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@varbear shared a link, 2 weeks, 5 days ago
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Agentic Coding is a Trap

AI-driven coding agents are the hot new trend, but beware of the trade-offs: increased complexity, skills atrophy, vendor lock-in, and fluctuating costs. Only skilled developers can spot issues in the vast lines of generated code, but paradoxically, AI tools are impacting critical thinking skills ne.. read more  

Agentic Coding is a Trap
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@varbear shared a link, 4 weeks ago
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Why are top university websites serving p0rn? It comes down to shoddy housekeeping.

Researcher Alex Shakhov found scammers commandeering staleCNAMErecords. They hijack university subdomains (eg.berkeley.edu,columbia.edu,washu.edu) and serve p0rn and scam pages. Shakhov found hundreds of abused subdomains across at least34universities. He counted thousands of hijacked pages indexed .. read more  

Why are top university websites serving p0rn? It comes down to shoddy housekeeping.
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@varbear shared a link, 4 weeks ago
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How The Heck Does Shazam Work? (An Interactive Exploration)

A phone captures audio and runs aFast Fourier Transform (FFT)on short windows. It builds aspectrogramand extractspeaks. Nearby peak pairs form compacthashes(two frequencies + time delta). Aninverted indexmaps those hashes to songs, and timing validates matches. Most services run lookups onserversaga.. read more  

How The Heck Does Shazam Work? (An Interactive Exploration)
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@varbear shared a link, 4 weeks ago
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I Decompiled the White House's New App

A React Native app built withExpo SDK 54runsHermes. It talks to a WordPress REST backend and bundles a 5.5MB Hermes bytecode.Its WebView injects JavaScript to strip cookies, GDPR prompts, and paywall dialogs. The build includes OneSignal's fused-location pipeline, polling at 4.5 and 9.5 minutes and.. read more  

I Decompiled the White House's New App
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@varbear shared a link, 4 weeks ago
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PostgreSQL MVCC, Byte by Byte

PostgreSQL's MVCC stores two 32-bit XIDs per tuple -xminandxmax. The transaction snapshot decides visibility per tuple. Updates append new tuples and mark the old withxmax.VACUUMreclaims versions only when no active snapshot can see them. Long-runningREPEATABLE READsnapshots pin versions and cause b.. read more  

PostgreSQL MVCC, Byte by Byte
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@varbear shared a link, 4 weeks ago
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The AWS Lambda 'Kiss of Death'

A Galera writer node froze afterInnoDBundo history ballooned. PooledAWS Lambdaconnections left transactions open and pinned MVCC read views. The team killed stalled sessions, enabledinnodb_undo_log_truncate, and cappedinnodb_max_undo_log_size. They also set sessiontransaction_isolation=READ-COMMITTE.. read more  

The AWS Lambda 'Kiss of Death'