Make it yours.Save notes, decks & boards to your own library.

openstem

Explore

Spaces

My Library

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

Loading…

loading…

About Privacy Terms of Service© openstem

We use privacy-friendly product analytics (no session recording, PII masked) to improve OpenStem. Load analytics? Privacy Policy

openstem

Explore

Groups Favorites

Collections Notes Flashcards Quizzes Sketches Flowcharts Plots Molecules

Make it yours.Save notes, decks & boards to your own library.

Get started Sign in

Explore Groups Favorites

Software: explore STEM content (page 2 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

Loading…

Collection4 items

01Collaboration & PR Workflow

02Branching & Merging

03Software · L2 · Git & Dev Workflow: Resolving a Merge Conflict

+1 more

Software

Software · L2 · Git & Dev Workflow

@openstem

Software · L2 · Git & Dev Workflow

Collection2 items

01TDD & Coverage

02Test Architecture & Strategy

Software

Software · L3 · Testing

@openstem

Software · L3 · Testing

Quiz6 questions

What guarantee does the subset construction (Rabin & Scott, 1959) provide?

AEvery NFA can be converted to an equivalent DFA, possibly with up to 2^n states for an n-state NFABEvery DFA can be converted to a smaller NFA in polynomial timeCNFAs recognise a strictly larger class of languages than DFAsDThe subset construction reduces the number of states in every case

Software

Software · L5 · Automata Theory & Formal Languages

@openstem

Software · L5 · Automata Theory & Formal Languages

Flowchart15 objects

Software

Software · L2 · Node.js: HTTP Middleware Pipeline · flowchart

@openstem

Software · L2 · Node.js: HTTP Middleware Pipeline · flowchart

Collection4 items

01HTTP Fundamentals

02TCP/IP & DNS

03Software · L1 · Networking & HTTP: Anatomy of a Web Request

+1 more

Software

Software · L1 · Networking & HTTP

@openstem

Software · L1 · Networking & HTTP

Collection4 items

01CAP & Consistency

02Caching

03Software · L2 · System Design: Choosing a Cache Strategy

+1 more

Software

Software · L2 · System Design

@openstem

Software · L2 · System Design

Flowchart18 objects

Software

Software · L1 · Security & Auth: Login & Session Flow · flowchart

@openstem

Software · L1 · Security & Auth: Login & Session Flow · flowchart

Flashcards9 cards

What is a Union-Find (Disjoint Set Union) data structure and what is its amortized complexity?1 / 9

Union-Find tracks disjoint sets. `find(x)` returns the root of x's set; `union(x, y)` merges sets. With path compression + union by rank, both ops are amortized O(α(n)) — inverse Ackermann, practically O(1).

Software

Advanced Structures

@openstem

Advanced Structures

Flowchart12 objects

Software

Software · L2 · MongoDB: Replica Sets & Failover · flowchart

@openstem

Software · L2 · MongoDB: Replica Sets & Failover · flowchart

Flashcards10 cards

What is a software design pattern?1 / 10

A reusable, named solution to a recurring design problem in a given context. A pattern is not a finished piece of code but a template/blueprint describing how to structure classes and objects to solve the problem.

Software

Pattern Fundamentals

@openstem

Pattern Fundamentals

Flashcards10 cards

What is the difference between hashing and encryption?1 / 10

Hashing is one-way — you cannot reverse a hash to the original (used for passwords, integrity). Encryption is two-way — ciphertext can be decrypted with a key (used for confidentiality). Never 'encrypt' passwords; hash them with a slow algorithm like bcrypt/Argon2.

Software

Cryptography Basics

@openstem

Cryptography Basics

Quiz5 questions

What is the correct order of steps when loading a fresh HTTPS page?

ATLS handshake, DNS lookup, TCP handshake, HTTP requestBDNS lookup, TCP handshake, TLS handshake, HTTP requestCHTTP request, DNS lookup, TCP handshake, TLS handshakeDTCP handshake, HTTP request, DNS lookup, TLS handshake

Software

Software · L1 · Networking & HTTP: Request Anatomy Check

@openstem

Software · L1 · Networking & HTTP: Request Anatomy Check

Flashcards11 cards

What concurrency granularity does the WiredTiger storage engine provide?1 / 11

Document-level concurrency control: concurrent writes to different documents in the same collection don't block each other. WiredTiger uses optimistic concurrency, detecting write conflicts at commit; on a conflict MongoDB transparently retries the operation.

Software

Storage Engine, Indexing & Query Internals

@openstem

Storage Engine, Indexing & Query Internals

Flashcards10 cards

What is the first rule of ARIA?1 / 10

Do not use ARIA if a native HTML element with the needed semantics and behavior already exists; prefer a real <button> over a <div role="button">.

Software

Accessibility & ARIA

@openstem

Accessibility & ARIA

Note~189 words · 1 min

From Creation to Termination Every process moves through a small set of states as the OS scheduler and I/O subsystem manage it. Learning these states makes it much easier to reason about what 'the CPU is busy' or 'the program is stuck' actu

Software

Software · L1 · Operating Systems: The Process Lifecycle

@openstem

Software · L1 · Operating Systems: The Process Lifecycle

Collection2 items

01Engine Internals

02Concurrency & Advanced Patterns

Software

Software · L4 · JavaScript

@openstem

Software · L4 · JavaScript

Flashcards10 cards

How is a TypeORM entity defined?1 / 10

A class annotated with `@Entity` whose properties use column decorators like `@PrimaryGeneratedColumn` and `@Column`, mapping to a table.

Software

Database & TypeORM

@openstem

Database & TypeORM

Flowchart11 objects

Software

Software · L4 · Concurrency patterns and pitfalls · flowchart

@openstem

Software · L4 · Concurrency patterns and pitfalls · flowchart

Quiz5 questions

Why do unit tests run before integration tests in the PR pipeline?

AIntegration tests can't run without unit tests existing firstBUnit tests are faster, so failing fast on them avoids wasting time on slower checksCUnit tests replace the need for integration testsDThere's no particular reason for the order

Software

Software · L2 · Testing: CI Test Execution Strategy

@openstem

Software · L2 · Testing: CI Test Execution Strategy

Flashcards8 cards

What does a service mesh add on top of plain service-to-service HTTP calls?1 / 8

A service mesh injects a sidecar proxy next to each service instance to handle cross-cutting concerns transparently: mTLS encryption, retries, timeouts, load balancing, circuit breaking, and traffic shaping (canary splits) — all without the application code knowing about it. The control plane configures every sidecar's routing rules and collects telemetry centrally.

Software

Microservices Architecture & Resilience Patterns

@openstem

Microservices Architecture & Resilience Patterns

Flashcards10 cards

What is the CAP theorem?1 / 10

A distributed system can guarantee at most two of: Consistency (all nodes see the same data), Availability (every request gets a response), Partition tolerance (works despite network splits). Since partitions are unavoidable, the real trade-off is CP vs AP.

Software

CAP & Consistency

@openstem

CAP & Consistency

Flashcards9 cards

How does Go conventionally handle errors?1 / 9

Functions return an `error` as the last return value, and callers check `if err != nil`. Errors are ordinary values, not exceptions, making control flow explicit.

Software

Errors & Idioms

@openstem

Errors & Idioms

Flashcards10 cards

What is the difference between SQL and NoSQL databases?1 / 10

SQL (relational): structured schemas, ACID transactions, joins. Good for complex queries and strong consistency. NoSQL (document, key-value, column, graph): flexible schemas, horizontal scaling, eventual consistency. Trade consistency/flexibility for scale.

Software

Databases & Storage

@openstem

Databases & Storage

Quiz5 questions

What does the `=======` marker separate inside a conflicted file?

ATwo unrelated filesBYour current branch's version from the incoming branch's versionCStaged changes from unstaged changesDCommit messages from diffs

Software

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

@openstem

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

Flashcards10 cards

What is the difference between L4 and L7 load balancing?1 / 10

L4 (transport layer) load balancing routes based on IP and TCP/UDP port — fast, simple, no protocol awareness. L7 (application layer) routes based on HTTP headers, URLs, cookies, or content — enables sticky sessions, path-based routing, and more sophisticated traffic management.

Software

Scalability & Reliability

@openstem

Scalability & Reliability

Quiz5 questions

Which service orchestrates the overall CI/CD workflow across stages?

ACodePipelineBCodeBuildCCodeDeployDCloudFormation

Software

Software · L2 · AWS: CI/CD Pipelines

@openstem

Software · L2 · AWS: CI/CD Pipelines

Note~209 words · 1 min

Untyped λ-Calculus The untyped λ-calculus (Church 1936) has three term forms: variables x, abstractions λx.M (anonymous functions), and applications (M N). The only computation rule is β-reduction: Substitute N for all free occurrences of x

Software

Software · L5 · Type Theory and the λ-Calculus

@openstem

Software · L5 · Type Theory and the λ-Calculus

Collection4 items

01Authentication & Authorization

02Security Fundamentals

03Software · L1 · Security & Auth: Login & Session Flow

+1 more

Software

Software · L1 · Security & Auth

@openstem

Software · L1 · Security & Auth

Flashcards10 cards

How does a WebSocket connection start?1 / 10

It begins as an HTTP request with an Upgrade: websocket header; if the server accepts (101 Switching Protocols), the connection switches to a persistent full-duplex WebSocket.

Software

WebSockets & Real-time

@openstem

WebSockets & Real-time

Flashcards10 cards

What does `FutureBuilder` do?1 / 10

It rebuilds its widget subtree based on the latest snapshot of a Future, exposing connection state, data, and error so you can render loading, success, and failure UIs.

Software

Async & Networking

@openstem

Async & Networking

‹ PrevPage 2 of 25Next ›