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Software: explore STEM content (page 8 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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Flowchart9 objects

Software

Software · L2 · System Design: Choosing a Cache Strategy · flowchart

@openstem

Software · L2 · System Design: Choosing a Cache Strategy · flowchart

Flowchart11 objects

Software

Software · L2 · Security & Auth: Incident Response Basics · flowchart

@openstem

Software · L2 · Security & Auth: Incident Response Basics · flowchart

Flowchart17 objects

Software

Software · L4 · Sharded write path with leader-follower replication

@openstem

Software · L4 · Sharded write path with leader-follower replication

Flashcards10 cards

What does JSX compile to?1 / 10

JSX is syntactic sugar for `React.createElement(type, props, ...children)` (or the new JSX transform's `_jsx`). The compiler converts angle-bracket syntax into nested function calls.

Software

JSX & Components

@openstem

JSX & Components

Flashcards9 cards

What does this print and why is it surprising?1 / 9

Prints `[1]` then `[1, 2]`. Default mutable arguments are evaluated ONCE at function definition, not per call — the same list persists across calls. Fix: use `def add(x, lst=None): if lst is None: lst = []`.

Software

Gotchas & Edge Cases

@openstem

Gotchas & Edge Cases

Flashcards10 cards

Why won't a surrounding try/catch catch an error thrown inside an async callback?1 / 10

The callback runs later on a separate stack after try/catch has already exited, so the throw escapes it; errors must be handled via the callback's error argument or an 'error' event.

Software

Error Handling & Debugging

@openstem

Error Handling & Debugging

Flowchart11 objects

Software

Software · L2 · Go: Choosing a Concurrency Primitive · flowchart

@openstem

Software · L2 · Go: Choosing a Concurrency Primitive · flowchart

Flashcards5 cards

What is a computer?1 / 5

A computer is a machine that follows instructions. It can store, find, and use information very fast.

Software

Software · L1 · What Is a Computer?

@openstem

Software · L1 · What Is a Computer?

Flashcards10 cards

What does a `record` declaration give you?1 / 10

A record is a transparent, immutable data carrier: the compiler generates a canonical constructor, private final fields, accessors, and value-based equals/hashCode/toString from the component list. It is ideal for DTOs and value objects.

Software

Modern Java & Memory Model

@openstem

Modern Java & Memory Model

Note~151 words · 1 min

Same Goal, Different Tools All synchronization primitives exist to keep concurrent access to shared state correct, but they differ in how many threads they let through at once, whether they track ownership, and whether they block or spin wh

Software

Software · L2 · Concurrency: Choosing a Synchronization Primitive

@openstem

Software · L2 · Concurrency: Choosing a Synchronization Primitive

Collection2 items

01Test Architecture & Test Doubles

02Determinism, Flakiness & CI Scale

Software

Software · L4 · Testing

@openstem

Software · L4 · Testing

Flashcards10 cards

What is the primary defense against SQL injection?1 / 10

Parameterized queries (prepared statements) keep user input as data, never as executable SQL, so the input cannot alter query structure.

Software

OWASP & Injection Attacks

@openstem

OWASP & Injection Attacks

Flashcards10 cards

What does a LEFT JOIN return for unmatched right-side rows?1 / 10

All rows from the left table, with NULLs in the right-table columns where no match exists.

Software

Joins & Subqueries

@openstem

Joins & Subqueries

Flashcards10 cards

What are the pillars of the AWS Well-Architected Framework?1 / 10

The framework has six pillars: Operational Excellence, Security, Reliability, Performance Efficiency, Cost Optimization, and Sustainability.

Software

Well-Architected & Resilience

@openstem

Well-Architected & Resilience

Note~92 words · 1 min

When Git Can't Auto-Merge A conflict means two branches changed the same lines and Git needs a human to decide the outcome. It marks the disputed section directly in the file rather than guessing. Staging a file with `git add` after editing

Software

Software · L2 · Git & Dev Workflow: Resolving a Merge Conflict

@openstem

Software · L2 · Git & Dev Workflow: Resolving a Merge Conflict

Collection2 items

01Async & Promises

02Performance & Memory

Software

Software · L3 · JavaScript

@openstem

Software · L3 · JavaScript

Quiz5 questions

Which GCP service is object storage accessed over HTTP?

ACloud StorageBPersistent DiskCFilestoreDCloud SQL

Software

Software · L1 · Google Cloud: Storage & Database Options

@openstem

Software · L1 · Google Cloud: Storage & Database Options

Flashcards10 cards

What is TypeScript and what problem does it solve?1 / 10

TypeScript is a statically typed superset of JavaScript that compiles to plain JS. It catches type errors at compile time rather than runtime, makes refactoring safer, and improves IDE support through autocompletion and inline docs.

Software

Types & Inference

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Types & Inference

Flashcards10 cards

What is the difference between INNER JOIN and LEFT JOIN?1 / 10

INNER JOIN returns only rows with matches in both tables. LEFT JOIN returns all rows from the left table, with NULLs for unmatched right-side columns. Use LEFT JOIN to keep rows that have no match.

Software

Joins

@openstem

Joins

Flashcards10 cards

What problem does the Raft consensus algorithm solve?1 / 10

Raft achieves consensus in a distributed cluster — agreement on a replicated log even when some nodes crash or are slow. It elects a leader via randomized election timeouts, and the leader serializes all writes, replicating to a majority quorum before committing.

Software

Distributed Systems Deep Dive

@openstem

Distributed Systems Deep Dive

Flashcards10 cards

What is the difference between @Controller and @RestController?1 / 10

@Controller returns view names (for server-side templates). @RestController = @Controller + @ResponseBody, so methods return data serialized directly to JSON/XML in the response body — the standard for REST APIs.

Software

Web & REST Controllers

@openstem

Web & REST Controllers

Collection4 items

01Web Protocols

02Cookies, Sessions & Auth

03Software · L2 · Networking & HTTP: OAuth 2.0 Authorization Code Flow

+1 more

Software

Software · L2 · Networking & HTTP

@openstem

Software · L2 · Networking & HTTP

Note~811 words · 4 min

Hoare Triples A Hoare triple {P} C {Q} states partial correctness: starting from any state satisfying precondition P, IF command C terminates, the resulting state satisfies postcondition Q. Partial correctness is deliberately silent on term

Software

Software · L5 · Hoare Logic & Program Verification

@openstem

Software · L5 · Hoare Logic & Program Verification

Collection2 items

01Concurrent React & Internals

02Patterns & Architecture

Software

Software · L4 · React

@openstem

Software · L4 · React

Flashcards10 cards

Are Java Stream operations eager or lazy?1 / 10

Intermediate operations like `map` and `filter` are lazy and only build a pipeline; processing happens when a terminal operation (e.g. `collect`, `forEach`) is invoked.

Software

Streams & Functional

@openstem

Streams & Functional

Flashcards10 cards

Why are indexes important in MongoDB?1 / 10

Without an index, a query does a full collection scan (O(n)). Indexes (B-tree) let MongoDB locate matching documents quickly. Index fields used in query filters and sorts. Like any DB, indexes speed reads but slow writes and use memory.

Software

Indexes & Scaling

@openstem

Indexes & Scaling

Collection4 items

01API Design & REST

02Software · L3 · API Design & REST

03Software · L3 · Choosing an HTTP Method and Status Code

+1 more

Software

Software · L3 · API Design & REST

@openstem

Software · L3 · API Design & REST

Flashcards10 cards

What memory model do Dart isolates use?1 / 10

Each isolate has its own memory heap and event loop and shares no mutable state with other isolates. They communicate only by passing messages over ports, which avoids data races and locks.

Software