Rust

Atomic File Write (tempfile + persist)

Write to a temp file in the SAME directory, then atomically `persist` (rename). The `tempfile` crate handles cleanup if you crash before persisting.

5h ago 0

Go

JSON API Endpoint

Decode an incoming JSON body into a typed struct, do work, encode a JSON response. The whole roundtrip is ~20 lines of standard library.

5h ago 0

Java

Atomic File Write (move with ATOMIC_MOVE)

Write to a temp file in the same directory, then `Files.move` with `ATOMIC_MOVE` to the target. Readers never see a half-written file — critical for config / state files.

5h ago 0

PHP

Atomic File Write

Write a file in a way that other processes never see a half-written state. Write to a temp file in the same directory, then rename — rename is atomic on POSIX filesystems.

5h ago 0

Bash

Associative Array (hash map)

Bash 4+ supports key-value associative arrays. Must `declare -A` first — Bash won't infer it. Iterate keys with !arr[@].

5h ago 0

SQL

Recursive CTE — Date Spine Generator

Generate a row per day (or month, year, hour) without a calendar table. Useful for filling gaps when a date has no events but you still want it in your output.

5h ago 0

Bash

SSH to Multiple Hosts in Parallel

Run the same command on a fleet of hosts. Three patterns: serial loop (simplest), GNU parallel (fastest), pssh (purpose-built).

5h ago 0

Rust

axum with Shared State + Extractors

Use `State` to inject shared application state (DB pool, config, etc.) into every handler. `Path` and `Json` extractors deserialize URL params and request bodies for you.

5h ago 0

JavaScript

Memoize Function

Caches the result of a pure function keyed by its serialised arguments. On repeated calls with the same inputs the cached value is returned instantly, skipping expensive computation. Supports single and multi-argument functions via JSON key serialisation.

5h ago 0

JavaScript

Format Relative Time

Returns a human-readable relative time string ("3 days ago", "in 2 hours") using the Intl.RelativeTimeFormat API. Automatically selects the most appropriate unit (seconds, minutes, hours, days, weeks, months, years) based on the elapsed time. Fully localised — pass any BCP 47 locale.

5h ago 0

JavaScript

Rate Limiter (Token Bucket)

Implements a token-bucket rate limiter that allows a burst of calls up to a maximum capacity, then replenishes tokens at a steady rate. Useful for throttling outbound API requests, user-facing actions, or any operation where you need to allow occasional bursts without exceeding a sustained rate.

5h ago 0

JavaScript

Random Hex Color

Generates a random 6-digit hex colour string. Useful for seeding avatar backgrounds, chart series colours, placeholder UI elements, and testing colour-dependent components. The crypto version produces a more unpredictable result suitable for generating unique palette tokens.

5h ago 0

PHP

Hash Large File Without Loading It

Compute the SHA-256 of a multi-gigabyte file by streaming it through hash_init / hash_update_stream — no memory blow-up. Useful for backup verification or torrent-style integrity checks.

5h ago 0

Java

Functional Interfaces — Function / Predicate / Consumer / Supplier

The four core single-method interfaces in `java.util.function`. They're the parameter types for streams, Optional methods, CompletableFuture, and countless library APIs.

5h ago 0

PHP

Generate Crypto-Strong Password

Generate a strong random password with configurable length and character sets. Uses rejection sampling to keep the distribution uniform across the chosen alphabet (no biased % alphabetLen).

5h ago 0

PHP

Validate IP Address (v4 + v6)

Distinguish IPv4 from IPv6, optionally reject private/reserved/loopback ranges. Useful for hardening server-side fetchers against SSRF.

5h ago 0

PHP

CSRF Token Generate + Verify

Per-session CSRF token helpers using hash_equals for constant-time comparison. Token is regenerated on logout but persists across requests within a session.

5h ago 0

Rust

Option Combinators (no unwrap!)

`Option<T>` has a rich combinator API that lets you avoid both `unwrap()` and the verbose `match`. Chain `map`, `and_then`, `unwrap_or`, `or_else` to compose fallible operations.

5h ago 0

PHP

Memoize a Function's Result

Cache the result of an expensive pure function by its arguments. Returns a closure with the same call signature that only invokes the inner function once per unique argument set.

5h ago 0

TypeScript

Promisify a Callback Function

Convert a Node-style `(err, result)` callback API into a Promise-returning function. Type-safe via generics — the inferred Promise resolves to the original callback's result type.

5h ago 0

TypeScript

Promise with Timeout

Race a promise against a timeout — if the work takes longer than `ms`, reject with a timeout error. Cancels nothing on its own (use AbortController for that), but unblocks the caller.

5h ago 0

Go

Table-Driven Tests with t.Run

A table of test cases looped through `t.Run` gives every case its own name in the output, makes adding new cases trivial, and lets you run individual cases with `-run TestX/case_name`.

5h ago 0

Go

Pointers — When and Why

Use pointers when you want to mutate the callee's value, share a large struct without copying, or distinguish "no value" via nil. Go has no pointer arithmetic — much safer than C.

5h ago 0

Rust

Fan-Out with try_join_all

Run N async operations concurrently and collect every Result. Fails fast on the first error; `join_all` is the variant that always waits for everyone.

5h ago 0

Rust

Format Strings (println! / write!)

Rust's format macros take an inline format string with `{}` placeholders. Named arguments, alignment, precision, debug formatting — all in the format spec.

5h ago 0

PHP

HMAC Webhook Signature Verify

Verify an inbound webhook (Stripe / GitHub / etc.) is genuine using HMAC-SHA256 and a shared secret. Includes timestamp tolerance to block replay attacks.

5h ago 0

Go

Custom Error Type with Fields

Implement the `error` interface (`Error() string`) on your own type to carry structured data. Pair with `errors.As` so callers can extract the fields.

5h ago 0

Python

asyncio.gather with Errors Tolerated

`gather(*tasks)` cancels everything on the first failure — usually NOT what you want. `return_exceptions=True` lets every task finish, returning the exception in place of a result. Perfect for fan-out HTTP fetches.

5h ago 0

Rust

Async Timeout

Wrap any future in `tokio::time::timeout` to fail it if it takes too long. Returns `Err(Elapsed)` on timeout; you decide what to do next (retry, fall back, propagate).

5h ago 0

TypeScript

Throttle (leading-edge, typed)

Pair to debounce: fire on the first call, then ignore further calls for `interval` ms. Useful for rate-limiting scroll handlers or button clicks.

5h ago 0