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The 300-Year Unbreakable Cipher That Got Broken — Vigenère, Enigma, and What Every "Unbreakable" Cipher Has in Common
Mobile-First Indexing: Why It's a Non-Event for Responsive Sites and a Real Risk for Separate Mobile Domains
Mobile-first indexing means Googlebot primarily indexes the mobile version of your content — even for desktop search results. For responsive sites, this is largely a non-event. For sites with separate mobile domains, dynamic serving, or aggressive mobile-specific lazy-loading, content/structured-data parity gaps between mobile and desktop versions become the version that's actually indexed.
Y2K, Y2K38, and Excel's 1900 Leap Year Bug: The Dates That Break Software
Y2K cost $300–600 billion to mitigate. The Unix 2038 problem will overflow signed 32-bit timestamps on 19 January 2038. Excel has counted 29 February 1900 as a real date since the 1980s. Here's the structural causes of each date bug and which ones are still ticking.
Recipe Scaling: Why Salt, Leavening, and Baking Time Don't Just Double When Your Recipe Does
Doubling a recipe doesn't mean doubling every ingredient by the same factor — salt and spices that taste "right" at 1x can taste over-seasoned at a linearly-doubled 2x, leavening agents commonly scale by 75-90% rather than 100%, and baking time scales by far less than 2x because heat penetration relates to thickness squared, not to volume. Here's why each of these deviates from linear scaling, and why pan-size choice is inseparable from baking-time expectations.
Gauge Pressure vs Absolute Pressure: Why Almost Every Pressure Reading You See Is Actually a Difference
A tyre gauge reads "0" on a completely flat tyre — not "-14.7 PSI," which is what it would show if it were truly measuring zero pressure. This is gauge pressure: nearly every everyday pressure reading (tyres, blood pressure) is actually a difference from atmospheric pressure, not an absolute amount. Here's what absolute pressure means by contrast, why weather/barometric readings and gas-law calculations require absolute pressure specifically, and the subtle way altitude affects gauge readings independent of temperature.
Structured JSON Logging: How to Debug Production API Errors and Search Logs at Scale
Structured JSON logs are queryable across millions of events in milliseconds; unstructured string logs require brittle grep. Here's why JSON logging matters, the OpenTelemetry log schema standard, structured logging libraries in Python/Node/Go, and how formatting API error responses reveals everything needed to debug a production incident.
What Developers Still Get Wrong About Password Storage in 2024
LinkedIn stored 117 million passwords as unsalted SHA-1 — cracked within days. Adobe used 3DES encryption (reversible) instead of hashing. These are the specific, named password storage mistakes that keep producing data breaches. Here's every common error, why it fails, and the correct modern approach with bcrypt and Argon2.
How File Hash Verification Actually Works: Determinism, the Avalanche Effect, and What "Match" Really Means
Hashing the same file twice, a year apart, on different computers, produces the exact same hash — this single property, determinism, is the foundation of file-integrity verification. Here's how the avalanche effect guarantees "match or no match, with no partial credit," why fixed output size makes hash comparison practical for huge files, the proper download-verification workflow, and why where a published hash comes from matters as much as the comparison itself.
IEEE 754 Floating-Point: Why 0.1 + 0.2 ≠ 0.3 and What to Use for Financial Calculations
0.1 + 0.2 ≠ 0.3 in nearly every programming language — because 0.1 can't be represented exactly in binary. Here's the IEEE 754 bit structure (sign, exponent, mantissa), special values (NaN, Infinity, -0), why integers above 2^53 lose precision in JavaScript, and why financial code should never use floats.
UUID Primary Keys in PostgreSQL, MySQL, and MongoDB: Performance Differences and Implementation Patterns
PostgreSQL stores UUIDs as 16-byte native types with no performance penalty. MySQL's InnoDB clustered index makes random UUID v4 fragmentation far worse than in PostgreSQL. MongoDB's ObjectId is 12 bytes with an embedded timestamp. Here's how UUID primary keys actually behave in each database and the ORM patterns to use them correctly.
DNS over HTTPS: Why Your Browser and Your DNS Lookup Tool Might Be Talking to Different Servers
Your computer's DNS settings and your browser's actual DNS resolution might be using completely different servers — DNS over HTTPS (DoH), increasingly implemented at the browser level, can bypass OS-level DNS settings entirely. Here's why DoH/DoT exist (encrypting DNS queries for privacy), why "dig shows the new record but my browser doesn't" can happen due to separate resolver caches, and how DoH interacts with network-level DNS filtering.
1000VA Isn't 1000W: Power Factor and Why UPS Sizing Often Goes Wrong
A UPS rated "1000VA" and a power supply rated "1000W" sound like the same quantity — they're not. VA (apparent power) and W (real power) differ by the power factor, and many common devices have power factors well below 1.0, meaning a "1000VA" UPS often can't actually support 1000W of real load. Here's what power factor means, why UPS units are rated in VA in the first place, why "naive" sizing (treating VA and W as interchangeable) can leave far less headroom than expected, and how active PFC closes the gap in modern equipment.
Morse Code Timing: Why "Faster" Means Rescaling Five Different Things at Once
A Morse code message can be sent anywhere from 5 to 40+ words per minute — but unlike typing speed, "faster" doesn't mean "the same dots and dashes, sooner." Every timing element (dot, dash, and three different gap types) is defined as a ratio relative to a single unit, and that unit scales together across all five elements at once. Here's how WPM is calibrated using the word "PARIS," why high-speed Morse becomes a perceptual rather than counted skill, and why Farnsworth timing deliberately breaks the proportional system for learners.
