Java

JUnit 5 — Basic Test

JUnit 5 is the modern standard. `@Test` marks a method as a test; `Assertions.*` provides the assertion API. `@BeforeEach` runs setup before every test.

38m ago 0

Java

Semaphore — Bounded Concurrency

Limit how many threads can enter a critical section. `acquire()` blocks until a permit is available; `release()` returns one. Use for rate limits, connection pools, or any "max N at a time" pattern.

38m ago 0

Go

json.RawMessage — Deferred Decoding

`json.RawMessage` is a `[]byte` that survives a decode pass. Use it for envelope-style JSON where one field's type depends on another (e.g. `{"type":"X","payload":{...}}`).

38m ago 0

Go

sync.Pool — Reuse Allocations

`sync.Pool` keeps a pool of reusable objects to reduce allocator pressure in hot paths. Good for byte buffers, JSON encoders, or anything you allocate frequently and only need briefly.

38m ago 0

Bash

ANSI Color Output Helpers

Wrap printf with ANSI escape codes for color and bold. Auto-disable if stdout isn't a TTY (so piping to a file doesn't pollute it with escape sequences).

38m ago 0

Python

group_by — Group Items by a Key

A dict-returning groupby that doesn't require sorted input. Like itertools.groupby but materializes the groups so consumers can iterate them multiple times.

38m ago 0

Bash

Multipart File Upload via cURL

Upload one or more files using -F. Optional extra form fields go through the same flag — quote carefully to preserve spaces.

38m ago 0

Kotlin

zip and zipWithIndex

`zip` pairs elements positionally; the result is the length of the shorter list. `withIndex()` gives you `(index, value)` pairs without the manual `forEachIndexed`.

38m ago 0

JavaScript

Fetch with Retry

Wraps the native fetch API with automatic retry logic using exponential backoff. Retries on network errors or non-OK HTTP responses up to a configurable number of attempts. Exponential backoff with optional jitter prevents thundering herd problems when many clients retry simultaneously.

38m ago 0

Bash

Symlink Force-Update

`ln -s` fails if the target already exists. `ln -sf` is the idempotent variant — useful in deploy scripts that point a "current" symlink to a fresh release directory.

38m ago 0

PHP

Resize Image to Max Dimension

Shrink an uploaded image so its longest side is no more than $maxDim pixels, preserving aspect ratio. Re-encodes to JPEG at the given quality. Uses the GD extension.

38m ago 0

Go

Empty Struct Sentinel (struct{})

`struct{}` is a zero-size value — no memory cost. Use it as the value type in a Set (`map[T]struct{}`), as a channel signal (`chan struct{}`), or as a marker type.

38m ago 0

Bash

Atomic File Write (write then rename)

Write to a temp file in the SAME directory, then `mv` to the final name. mv on the same filesystem is atomic — readers never see a half-written file.

38m ago 0

Python

Protocol — Structural (Duck) Typing

Define what an object can DO, not what it IS. A class doesn't need to inherit from a Protocol — it just needs to match the shape. Like TypeScript interfaces with `implements` optional.

38m ago 0

Go

Worker Pool with Channels

Spawn N worker goroutines, feed them tasks over a jobs channel, collect results on a results channel. Idiomatic Go pattern for bounded concurrency.

38m ago 0

Rust

anyhow for Application Errors

`anyhow::Result<T>` is `Result<T, anyhow::Error>` — a type-erased error that captures any other error AND adds context via `.context()`. The app-author's pick (use thiserror for libraries).

38m ago 0

Python

unique_everseen — Order-Preserving Dedupe

Remove duplicates while preserving original order (set() loses order on collisions). Optional key function lets you dedupe by a derived value — e.g., lowercased email.

38m ago 0

SQL

MERGE — One Statement for INSERT + UPDATE + DELETE

`MERGE` (standard SQL, PostgreSQL 15+, SQL Server, Oracle) is a single statement that combines INSERT/UPDATE/DELETE driven by joining a source against a target. Heavy artillery for reconciliation jobs.

38m ago 0

Python

Slugify (unicodedata, zero deps)

Convert any string to a URL-safe slug using only stdlib. Normalizes Unicode (NFKD), strips combining marks, lowercases, replaces non-alphanumerics with a separator.

38m ago 0

Kotlin

Variance — in vs out

`out T` (covariant) → producer of T; can be assigned to a wider type. `in T` (contravariant) → consumer of T; can be assigned to a narrower type. Without modifiers, generics are invariant (strict match).

38m ago 0

JavaScript

Parse URL Query String

Parses a URL query string into a plain key-value object. Uses the built-in URLSearchParams API — no regex required. Handles duplicate keys (returns the first value), percent-encoded characters, and works with both full URLs and raw query strings. Pairs nicely with buildQueryString.

38m ago 0

SQL

INSERT … SELECT — Bulk Copy

Copy/transform rows from a SELECT into another table — the cheapest way to move data within the database. Skip column lists at your peril; positional matching is fragile.

38m ago 0

Go

Sentinel Errors (var ErrFoo = errors.New)

Sentinel errors are package-level singletons you can compare against with `errors.Is`. Use sparingly — they're part of your package's API surface and changing them is a breaking change.

38m ago 0

Kotlin

Compose Modifier Chain

`Modifier` is how you customize composables — padding, click handlers, background, size, alignment. Order matters: each modifier wraps the previous one.

38m ago 0

Rust

impl Trait — Static Dispatch Returns

When you want to return a complex iterator chain or closure, you don't need to spell out the type. `impl Trait` lets the compiler infer the concrete type while exposing only the API contract.

38m 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.

38m ago 0

Go

Error Wrapping with %w

`fmt.Errorf` with `%w` wraps an inner error inside an outer one, preserving the chain. Callers can use `errors.Is` / `errors.As` to inspect any level of the chain.

38m ago 0

Kotlin

Sorting Collections

`sortedBy { ... }` returns a sorted copy. `sortedWith(compareBy { ... })` chains tie-breakers cleanly. Avoid `sortBy` (in-place) on read-only lists.

38m ago 0

Java

JUnit 5 — Parameterized Tests

`@ParameterizedTest` runs the same test with multiple inputs. Use `@CsvSource`, `@MethodSource`, or `@EnumSource` for data. Eliminates copy-paste in test classes.

38m ago 0

PHP

Stream Large CSV with Generator

Iterate over a CSV file row-by-row without ever loading the whole file into memory. Uses a generator so consumers can foreach naturally and PHP cleans up the file handle.

38m ago 0