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Software: explore STEM content (page 21 of 25) · openstem

All fields Software Mathematics Physics Chemistry Biology Engineering Astronomy Environmental Other Software Software groups

Explore STEM Content

Search the community's STEM library — free to study, yours to make your own.

Software

Programming, algorithms and systems on openstem — flashcards, notes, quizzes, sketches and flowcharts shared by the community. Study free, or clone anything into your library.

Content Groups1

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Flashcards9 cards

When would you add a cache and what are the main invalidation strategies?1 / 9

Add a cache when reads vastly outnumber writes and slight staleness is acceptable. Strategies: write-through (cache + DB together), write-back (write cache, flush later), TTL expiry, and cache-aside (app manages cache). Invalidation is the hard part.

Software

Caching

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Caching

Flashcards9 cards

What is a race condition?1 / 9

A bug where the program's correctness depends on the non-deterministic timing/interleaving of concurrent operations on shared mutable state — e.g. two threads incrementing a counter without synchronization can lose updates. Prevented with locks, atomics, or avoiding shared mutability.

Software

Fundamentals

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Fundamentals

Note~129 words · 1 min

Same Shape, Different Intent Adapter, Decorator, and Proxy all wrap one object behind an interface, which is exactly why they're easy to confuse. The difference is in what the wrapper is for: translating, extending, or controlling. A Decisi

Software

Software · L2 · Design Patterns: Which Structural Pattern?

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Software · L2 · Design Patterns: Which Structural Pattern?

Collection4 items

01Responsive & Modern CSS

02Accessibility & ARIA

03Software · L2 · HTML & CSS: Computing an Element's Accessible Name

+1 more

Software

Software · L2 · HTML & CSS

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Software · L2 · HTML & CSS

Flowchart13 objects

Software

Software · L1 · PostgreSQL: Full-Text Search · flowchart

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Software · L1 · PostgreSQL: Full-Text Search · flowchart

Flashcards10 cards

What library does Nest commonly use for authentication strategies?1 / 10

Passport, integrated via `@nestjs/passport`, with strategies like `passport-jwt` and `passport-local` wrapped as guards.

Software

Authentication & Middleware

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Authentication & Middleware

Note~126 words · 1 min

Passing a Value Without a Fight Every time you hand a value to a function or another variable, Rust makes you pick one of three strategies. Getting this choice right up front avoids most of the borrow-checker errors newcomers run into. Work

Software

Software · L1 · Rust: Move, Borrow, or Clone?

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Software · L1 · Rust: Move, Borrow, or Clone?

Collection2 items

01Gotchas & Edge Cases

02Performance & Internals

Software

Software · L3 · Python

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Software · L3 · Python

Flashcards10 cards

What command connects to a PostgreSQL database interactively?1 / 10

`psql -U <user> -d <database>` opens the interactive SQL terminal. Inside, `\dt` lists tables, `\d table` describes one, and `\q` quits.

Software

PostgreSQL Basics

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PostgreSQL Basics

Collection4 items

01Databases & Storage

02APIs & Protocols

03Software · L1 · System Design: Choosing a Database Type

+1 more

Software

Software · L1 · System Design

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Software · L1 · System Design

Flashcards10 cards

Describe the producer-consumer pattern and its synchronization requirements.1 / 10

Producers add items to a shared buffer; consumers remove and process them. Synchronization needed: (1) mutual exclusion on the buffer, (2) consumers wait when empty, (3) producers wait when full. Typically implemented with a bounded queue + condition variables or a channel.

Software

Concurrency Patterns

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Concurrency Patterns

Flashcards8 cards

Implement cycle detection in a linked list.1 / 8

Floyd's Tortoise & Hare: advance slow by 1 and fast by 2. If they meet, there's a cycle. O(n) time, O(1) space.

Software

Linked Lists

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Linked Lists

Flashcards10 cards

How is CSS specificity scored, and what beats what?1 / 10

Specificity is a tuple (inline, IDs, classes/attributes/pseudo-classes, elements). Compared left to right, a higher group wins. Inline styles outrank ID selectors, which outrank classes, which outrank type selectors.

Software

CSS Architecture & Modern Selectors

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CSS Architecture & Modern Selectors

Flashcards10 cards

How do you declare a variable whose type is inferred in Dart?1 / 10

Use `var` (mutable) or `final` (single assignment) and let Dart infer the type from the initializer, e.g. `var count = 0;` infers `int`.

Software

Dart for Flutter

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Dart for Flutter

Quiz3 questions

What does this Scratch-style code do? repeat 3 times: move forward 10 steps

AMoves forward 10 steps onceBMoves forward 3 stepsCMoves forward 30 steps in total (10 each time, 3 times)DDoes nothing

Software

Software · L2 · Loops, Conditionals, and Variables

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Software · L2 · Loops, Conditionals, and Variables

Flashcards10 cards

What are the three trees Flutter maintains for rendering?1 / 10

The Widget tree (immutable config), the Element tree (mutable instances linking widgets to render objects), and the RenderObject tree (handles layout and painting).

Software

Rendering Pipeline

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Rendering Pipeline

Collection4 items

01Unit Testing & Mocking

02Integration & E2E

03Software · L2 · Testing: CI Test Execution Strategy

+1 more

Software

Software · L2 · Testing

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Software · L2 · Testing

Note~133 words · 1 min

Two Ways to Model Relationships MongoDB gives you two basic strategies for related data: embed it as a subdocument inside the parent, or store it in a separate collection and reference it by _id. There's no single right answer — it depends

Software

Software · L1 · MongoDB: Schema Design — Embedding vs Referencing

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Software · L1 · MongoDB: Schema Design — Embedding vs Referencing

Note~809 words · 4 min

Turing Machines as the Formal Model of Computation A Turing machine is M = (Q, Σ, Γ, δ, q₀, q_accept, q_reject): a finite control Q, input alphabet Σ, tape alphabet Γ ⊇ Σ ∪ {⊔}, transition function δ: Q × Γ → Q × Γ × {L, R}, start state q₀,

Software

Software · L5 · Computability Theory

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Software · L5 · Computability Theory

Flashcards10 cards

What is the difference between `Box<T>`, `Rc<T>`, and `Arc<T>`?1 / 10

`Box<T>` is a single-owner heap allocation. `Rc<T>` is reference-counted shared ownership for single-threaded use. `Arc<T>` is the atomic, thread-safe version of Rc for sharing across threads (slightly more overhead).

Software

Memory & Smart Pointers

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Memory & Smart Pointers

Flashcards9 cards

What is a window function and how does it differ from GROUP BY?1 / 9

A window function computes a value across a set of rows (the 'window') without collapsing them into one row like GROUP BY does. Each input row gets an output row. `OVER (PARTITION BY ... ORDER BY ...)` defines the window.

Software

Window Functions

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Window Functions

Collection4 items

01Enums & Error Handling

02Traits & Generics

03Software · L2 · Rust: Option, Result, or panic!?

+1 more

Software

Software · L2 · Rust

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Software · L2 · Rust

Collection5 items

01Fundamentals

02Types & Coercion

03ES6+ Features

+2 more

Software

Software · L1 · JavaScript

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Software · L1 · JavaScript

Quiz8 questions

What is the primary benefit of moving cross-cutting network concerns into a service mesh sidecar?

AApplication code gets mTLS, retries, timeouts, and traffic shaping without implementing them itselfBIt removes the need for a network entirelyCIt eliminates the need for service-to-service authenticationDIt guarantees zero latency between services

Software

Software · L4 · Microservices Architecture & Resilience Patterns

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Software · L4 · Microservices Architecture & Resilience Patterns

Note~557 words · 3 min

Pure Functions and Side Effects A pure function's return value depends only on its arguments, and calling it has no observable effect beyond producing that value — no writing to a database, mutating a shared object, logging, or reading the

Software

Software · L3 · Functional Programming Concepts

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Software · L3 · Functional Programming Concepts

Flashcards10 cards

What is the difference between Dart's JIT and AOT compilation?1 / 10

JIT compiles at runtime (used in development for hot reload and fast iteration), while AOT compiles ahead of time to native machine code (used in release builds for fast startup and predictable performance).

Software

VM, AOT/JIT & Performance

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VM, AOT/JIT & Performance

Flowchart28 objects

Software

Software · L5 · From SQL Query to Physical Plan

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Software · L5 · From SQL Query to Physical Plan

Quiz10 questions

What is a race condition?

ATwo threads finishing at the same timeBA bug where the outcome depends on the relative timing or interleaving of concurrent operationsCA performance optimisation that speeds up parallel codeDA deadlock involving exactly two threads

Software

Software · L4 · Concurrency & parallelism — 10 Q

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Software · L4 · Concurrency & parallelism — 10 Q

Note~154 words · 1 min

Transform, Don't Mutate JavaScript arrays ship two families of methods: ones that return a new array (map, filter, slice) and ones that mutate in place (push, splice, sort). Reaching for the non-mutating family by default keeps data flow pr

Software

Software · L1 · JavaScript: Array Method Choices

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Software · L1 · JavaScript: Array Method Choices

Flowchart11 objects

Software

Software · L4 · Big-O complexity cheat sheet · flowchart

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Software · L4 · Big-O complexity cheat sheet · flowchart

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