The author discovered that someone was intercepting and replaying his web traffic, which indicated his home network or modem had been compromised. After investigating, he found the IP address belonged to DigitalOcean and had previously been used for phishing and malware campaigns. The author was unable to keep the potentially compromised modem when getting a replacement, so he had to give it back to his ISP, Cox. Years later, the author's cybersecurity friends looked into the incident further and discovered the IP address was part of a domain generation algorithm used by malware. They also found that the Cox business portal had an exposed API that could be used to access and control customer modems without authorization. The author reported the vulnerabilities to Cox, who quickly fixed the issues.

In April 2024, the author discovered and reported two critical bugs to the Sei Network blockchain. The first bug would have caused the chain to halt if exploited, while the second bug would have allowed an attacker to freely transfer funds out of any account. The Sei Foundation awarded the author $75,000 and $2,000,000 respectively for these reports. The issues were caught after auditing but before being deployed to mainnet, preventing any funds from being put at risk. The author provided detailed technical explanations of how the bugs worked and how they were ultimately fixed by the Sei team.

- TicketMaster has moved away from traditional printable PDF tickets in favor of a proprietary "SafeTix" system that uses rotating barcodes displayed on a mobile device.
- The rotating barcodes are meant to prevent ticket fraud, but the author argues they create significant usability issues, especially when cell service is poor at venues.
- TicketMaster markets SafeTix as a solution to ticket scalping and fraud, but the author believes the real motivations are to lock users into TicketMaster's ecosystem and make it harder to resell tickets outside their platform.
- The author was able to reverse engineer the SafeTix system and discovered it uses Time-based One-Time Passwords (TOTPs) along with a static bearer token to authenticate tickets.
- With the TOTP secrets and bearer token, the author could theoretically generate valid barcodes and bypass TicketMaster's security measures.
- TicketMaster makes it easy to extract the necessary token information by printing it to the browser console when the barcode is loaded.
- The author is uncertain about the lifetime of the TOTP tokens, but believes they may only be valid for up to 20 hours before the event based on TicketMaster's documentation.
- The author developed a tool called "TicketGimp" that can render valid SafeTix barcodes using the extracted token information.
- The author is highly critical of TicketMaster's practices, accusing them of using technology to exclude and disadvantage customers for their own financial gain.
- The author calls on TicketMaster's developers to have more integrity and use their technical skills responsibly, rather than enabling TicketMaster's "cruel business practices".

- Python has a fragmented package and environment management ecosystem, with over a dozen different tools, each with their own strengths and weaknesses.
- The lack of a standardized, efficient, and user-friendly package manager in Python has been an "inexcusable pain-in-the-ass" for many years.
- Other programming languages like Rust, C#, and JavaScript have developed more cohesive and widely-loved package management solutions like Cargo, NuGet, and npm.
- Python's legacy package manager pip has historically had poor dependency resolution, only recently adding backtracking capabilities. It also lacks environment management features.
- The proliferation of various configuration files like requirements.txt, setup.py, Pipfile, environment.yml etc. has led to a lot of redundancy and lack of standardization in Python package management.
- The introduction of PEP 621 in 2020 aimed to consolidate dependencies and configuration into a single pyproject.toml file, leading to the emergence of new tools like Poetry, PDM, Flit, and Hatch.
- Poetry is currently the closest Python tool to the Cargo experience, but it suffers from slow dependency resolution, especially for large projects.
- Conda is a popular choice for data scientists and experimentalists as it can manage non-Python dependencies, but it lacks some features like lock files and can be cumbersome for production use.
- The Rust community's influence is evident in promising new Python package management tools like uv, which aims to be a fast, Cargo-like drop-in replacement for pip.
- The Python community still lacks a cohesive, standardized, and widely-adopted package management solution, but tools like uv hold promise for the future.

- Developed by Umbra (CedarDB's predecessor)
- Adopted by DuckDB, Apache Arrow, Polars, and Facebook Velox

German Strings are a custom string type highly optimized for data processing. They offer significant improvements over traditional C and C++ string implementations.

Key Features:
- 128-bit struct representation (vs. 192 bits in C++)
- Short string optimization for strings ≤12 characters
- Long string format with 4-char prefix for quick comparisons
- Immutable design for better performance and concurrency
- Storage classes: persistent, transient, temporary

Advantages:
- Space-efficient, fitting in two CPU registers
- Reduced allocations and data movement
- Easier parallelization due to immutability
- Flexible lifetime management with storage classes
- Optimized for common database operations (comparisons, sorting)

Trade-offs:
- Requires careful consideration of string usage and lifetime
- Updates are more expensive (but rare in database systems)
- Maximum string length limited to 4 GiB

- The author was able to significantly optimize a byte-counting program, achieving a ~550x speedup over a naive implementation.
- The key optimization was using an interleaved memory access pattern, reading from different 4KB pages in a round-robin fashion, instead of sequential access.
- This interleaved access pattern takes advantage of the "Streamer" hardware prefetcher in modern CPUs, which can maintain separate forward and backward access streams for each 4KB page.
- Interleaving 8 different 4KB pages was found to be the optimal approach, providing up to a 30% performance boost over sequential access.
- The author also unrolled the inner loop to process 2 cache lines (64 bytes) at a time, and added a prefetch instruction to fetch the next set of data.
- The final solution uses AVX2 SIMD instructions to perform the byte counting in a highly efficient manner.
- The author was able to achieve a ranking of #13 on the HighLoad leaderboard with this optimized solution.
- The interleaved memory access pattern seems to be an under-discussed optimization technique, with the author not recalling seeing it used in other code.
- The author encourages readers to share any other memory-based optimizations they are aware of, as the author is interested in learning about them.
- The document provides the full source code for the optimized byte-counting program, allowing readers to study and potentially apply the techniques in their own work.

- The database was the central component of the system, with a table called "Merchants" that had over 500 columns due to running out of columns in the original "Merchants" table.
- The "SequenceKey" table was a single-column, single-row table used to generate IDs, demonstrating a creative but unconventional solution.
- The system had a manually maintained "calendar" table to track login access, which was a fragile and outdated approach.
- The employee data was reloaded from a CSV file every morning, with an email-based process to replicate the data to headquarters.
- There was a normalized copy of the database, but it required 7 joins to go from the "Merchants" table to a phone number, showing the complexity.
- The codebase was a mix of VB and C#, with a proliferation of JavaScript frameworks and custom modifications.
- The "shipping manager" application was built in a weekend by a single developer named Gilfoyle, who was known for not checking in his code.
- The author discovered a bug related to the shipping queue that was caused by a SOAP service client doing all the side effects instead of the service itself.
- The "Merchants Search" page was optimized by a senior developer named Justin, who was able to make significant improvements by decoupling the page into separate endpoints.
- The codebase, despite its flaws, allowed for a sense of freedom and creativity, with developers carving out their own "little worlds of sanity" within the larger monolithic application.

- Concurrency issues can be difficult to recognize and often get overlooked, leading to hard-to-debug bugs.
- It's tempting to dismiss concurrency issues due to perceived low likelihood, but they can still crop up unexpectedly under high load.
- Locking is a common approach to handling concurrency, but locks can be overused and lead to performance issues.
- The database is the lowest common denominator for coordinating locks across multiple processes and servers.
- The "ask for forgiveness" (EAFP) approach, where you try an operation and handle exceptions, is often more Pythonic than checking conditions in advance.
- In PostgreSQL, when an exception occurs within a transaction, it can block further commands until the transaction ends, requiring special handling.
- Using SELECT FOR UPDATE can lock rows to prevent race conditions, but this can also cause performance issues with high concurrency.
- Incrementing counters directly in the database, using an F expression, can avoid race conditions without the need for explicit locking.
- Combining database-level updates with RETURNING to immediately fetch the updated object can optimize the process further.
- The key is to keep concurrency issues in mind, avoid dismissing them due to perceived low likelihood, and use the most appropriate concurrency control mechanisms for the specific situation.