How Moiré Patterns Have Been Used to Guide Ships Safely into Port

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A technical article published on the Tinkerings blog explores the practical maritime application of moiré patterns for navigational guidance. Moiré patterns, created when two overlapping grids or lines produce a distinctive visual interference effect, can serve as precise alignment indicators. When viewed from a vessel, these patterns shift visibly depending on the observer's angle, allowing navigators to determine whether their ship is on the correct approach path. This optical principle has been applied in harbor and channel entry systems to help guide ships safely without electronic aids. The article highlights an elegant, low-tech solution to a real-world navigation challenge.

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Developer Builds Daily German Word WhatsApp Bot After Week of Automation Hurdles

A developer set out to create a simple WhatsApp Channel that posts one German vocabulary word each morning, but the project quickly grew complex due to WhatsApp's session management challenges. The initially chosen library, whatsapp-web.js, required a full Chromium browser profile to maintain login sessions, making cloud deployment impractical and causing repeated authentication failures. Hosting platforms added further complications, with Railway banning userbot-style automations and Render suffering from unreliable session restoration bugs. The breakthrough came from switching to the Baileys library, which communicates with WhatsApp over a WebSocket without needing a browser, reducing session data from 43MB to a few small JSON files. This single change resolved both the hosting and session problems, allowing the bot to run reliably on a free-tier server with credentials stored in a MongoDB Atlas cluster.

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ProgrammingDEV Community ·

Cron Has No Native Biweekly Option — But a Day-of-Month Trick Fills the Gap

Standard 5-field cron syntax has no built-in support for 'every 2 weeks,' leaving developers who need biweekly scheduling without an obvious solution. A common mistake is using expressions like '0 0 * * 1', which fires every Monday rather than every other Monday. A practical workaround combines day-of-month ranges with a weekday filter — for example, '0 0 1-7,15-21 * 1' reliably triggers once a fortnight on Mondays at midnight. However, windows ending near day 28 should be avoided as they can disappear in shorter months like February. For more complex biweekly logic, developers are advised to use a weekly cron trigger paired with a wrapper script, or switch to schedulers like APScheduler that support calendar-based intervals natively.

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ProgrammingHacker News ·

Programming Language Creators and Their Quirky Personal Homepages

A blog post on breck.lol explores the personal websites of notable programming language creators. The piece highlights the distinctive and often unconventional design choices these developers make for their own homepages. It drew modest attention on Hacker News, earning 9 points and 2 comments. The article offers an informal look at how the minds behind influential languages choose to present themselves online.

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ProgrammingDEV Community ·

What Are Serverless Cold Starts and How Do They Slow Your App Down

In serverless computing, a cold start is the latency that occurs when a cloud function is triggered after being idle, forcing the provider to spin up a container, load the code, and initialize the environment before executing. Unlike traditional servers running continuously, serverless functions only consume resources during execution, making them cost-efficient but vulnerable to unpredictable startup delays. These delays become problematic in real-world scenarios such as sudden traffic surges or infrequently accessed features, where users may experience multi-second lag spikes. A common mitigation technique involves placing resource-heavy operations like database connections in the global scope of the function, so they run only once during initialization and are reused across subsequent warm requests. Developers must balance the cost savings of serverless architecture against the user experience impact of cold starts by optimizing code structure, reducing deployment package size, and selecting appropriate runtime environments.

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