Production Bugs

Summary This incident examines why multiple [[no_unique_address]] fields of the same empty type do not overlap across a class hierarchy, even though the attribute suggests that empty subobjects may share storage. The expectation that S3 should be the same size as S1 is reasonable at first glance, but the C++ object model imposes strict rules … Read more

Summary Issue: Determining the current track index in a MediaListPlayer using python-vlc is non-trivial due to limitations in libvlc_media_list_index_of_item(). Root Cause Lack of Direct API: python-vlc does not provide a direct method to retrieve the current track index from a MediaListPlayer. Ambiguity in libvlc_media_list_index_of_item(): This function returns the first matched position, which is unreliable if … Read more

Summary This incident documents a failed attempt to build a “Recommended for You” movie feature using machine‑learning techniques without first establishing a stable baseline, clear evaluation metrics, or a reproducible experimentation workflow. The system produced inconsistent recommendations, poor ranking quality, and unpredictable behavior once deployed behind a Node.js API. Root Cause The primary root cause … Read more

Summary This incident analyzes memory imbalance in PolarDB PostgreSQL with IMCI enabled, where the RW node experiences significantly higher memory pressure than RO nodes due to row‑to‑columnar conversion overhead. The imbalance leads to RW OOM events during peak load, impacting service stability and query latency. Root Cause The core issue arises from IMCI’s row‑to‑columnar conversion, … Read more

Summary This postmortem analyzes why a seemingly valid PowerShell parameter‑set design fails to resolve when positional parameters overlap across sets. The failure stems from PowerShell’s parameter binder attempting to match all possible parameter sets simultaneously, leading to ambiguous interpretations even when a human believes the intent is obvious. Root Cause The root cause is parameter‑set … Read more

Summary This postmortem examines a common relational‑design failure: implementing Exclusive Arc (a.k.a. Polymorphic) relationships in PostgreSQL using multiple nullable foreign keys. The pattern works at first, but it becomes brittle, hard to extend, and difficult to enforce correctly. Senior engineers eventually replace it with cleaner, constraint‑friendly designs. Root Cause The root cause is the assumption … Read more

Summary Issue: Misunderstanding of database connection closure in PHP when using prepared statements. The developer was unsure if closing the prepared statement ($stmt->close()) also closes the database connection. Root Cause Confusion between prepared statement and database connection objects: The developer mistakenly assumed that closing the prepared statement ($stmt->close()) would also close the database connection ($mysqli). … Read more

Summary A SwiftUI toolbar using the new iOS 26 Liquid Glass animation only animates when its content changes rapidly. Under normal state changes—such as switching a segmented picker—the toolbar updates instantly with no morphing/materialize animation. This postmortem explains why this happens, why it’s expected in real systems, and how senior engineers work around it. Root … Read more