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OpenStem
@openstem · Joined Jul 2026
7420 public items8 groups
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.
Isolates & Concurrency
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Isolates & ConcurrencyFlashcards10 cards
What is the difference between a single-subscription and a broadcast Stream?1 / 10
A single-subscription stream allows only one listener over its lifetime and buffers events until then; a broadcast stream allows many simultaneous listeners and does not buffer for late subscribers.
Streams & Async Generators
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Streams & Async GeneratorsFlashcards10 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).
VM, AOT/JIT & Performance
@openstem
VM, AOT/JIT & PerformanceFlashcards10 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.
Async & Networking
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Async & NetworkingFlashcards10 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).
Rendering Pipeline
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Rendering PipelineFlashcards11 cards
What does `export const revalidate = 60` in a page do?1 / 11
It sets an Incremental Static Regeneration interval, so the cached page is regenerated at most once every 60 seconds when requested.
Caching & Revalidation
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Caching & RevalidationFlashcards10 cards
Where does Next.js middleware run?1 / 10
It runs before a request is completed — ahead of the matched route — letting you rewrite, redirect, or set headers/cookies before the route handles the request. In Next.js 16 the file/function is renamed from middleware to proxy (proxy.ts / export function proxy()), running on the Node.js runtime; the legacy edge `middleware` name is deprecated.
Middleware, Auth & Deployment
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Middleware, Auth & DeploymentFlashcards10 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.
Database & TypeORM
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Database & TypeORMFlashcards10 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.
Authentication & Middleware
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Authentication & MiddlewareFlashcards10 cards
When should you embed related data versus reference it?1 / 10
Embed when data is accessed together and bounded in size; reference when data is large, shared, or grows unbounded.
Schema Design & Modeling
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Schema Design & ModelingFlashcards10 cards
What is a MongoDB replica set?1 / 10
A group of mongod nodes maintaining the same data: one primary accepts writes and secondaries replicate the oplog for redundancy and failover.
Replication & Transactions
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Replication & TransactionsFlashcards10 cards
What does MVCC stand for and provide?1 / 10
Multi-Version Concurrency Control: readers see a consistent snapshot without blocking writers, and writers don't block readers.
Transactions & MVCC
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Transactions & MVCCFlashcards10 cards
What information does EXPLAIN ANALYZE give that plain EXPLAIN does not?1 / 10
EXPLAIN ANALYZE actually executes the query and reports actual rows returned, actual time per node, and loop counts, compared to EXPLAIN's estimate-only plan.
Performance Tuning
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Performance TuningFlashcards10 cards
What is AWS Lambda?1 / 10
Lambda is a serverless compute service that runs your function code in response to events without you provisioning or managing servers, billing per request and execution duration.
Serverless & Lambda
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Serverless & LambdaFlashcards10 cards
Which S3 storage class is cheapest for rarely accessed archival data with retrieval delays acceptable?1 / 10
S3 Glacier Deep Archive offers the lowest storage cost for long-term archives where retrieval times of hours are acceptable.
Storage & Content Delivery
@openstem
Storage & Content DeliveryFlashcards10 cards
What kind of system is BigQuery?1 / 10
BigQuery is a serverless, columnar, fully managed data warehouse that separates storage from compute and scales queries automatically.
Data & Analytics (BigQuery)
@openstem
Data & Analytics (BigQuery)Flashcards10 cards
In GKE, what is the difference between Standard and Autopilot modes?1 / 10
Standard mode lets you manage and pay for nodes directly. Autopilot manages nodes for you, billing per-Pod resource requests, reducing operational overhead and enforcing best-practice defaults.
Architecture & Scale
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Architecture & ScaleFlashcards10 cards
What is the core Terraform workflow order?1 / 10
terraform init (install providers/backend), then plan (preview changes), then apply (execute), with destroy to tear down.
Workflows & Best Practices
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Workflows & Best PracticesFlashcards10 cards
What is the main risk of a single monolithic Terraform state for a large org?1 / 10
Everything shares one lock and blast radius: plans get slow, a single apply can touch unrelated systems, and concurrent work is serialized. Split state by service/layer instead.
Advanced State & Scaling
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Advanced State & ScalingFlashcards9 cards
What does it mean for an HTTP method to be idempotent?1 / 9
Calling it once or many times with the same request produces the same server state as calling it once. GET, PUT, DELETE, HEAD, and OPTIONS are idempotent; POST is not.
API Design & REST
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API Design & RESTFlashcards8 cards
How does the cache-aside (lazy loading) pattern work?1 / 8
The application checks the cache first; on a miss, it reads from the database, then writes the result into the cache before returning it. Subsequent reads for the same key hit the cache until it expires or is evicted.
Caching Strategies
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Caching StrategiesFlashcards8 cards
What makes a function 'pure'?1 / 8
Its output depends only on its inputs (no reliance on external mutable state), and calling it causes no observable side effects (no I/O, no mutation of arguments or globals).
Functional Programming Concepts
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Functional Programming ConceptsFlashcards8 cards
How does a typical backtracking regex engine try to match a pattern?1 / 8
It tries alternatives and quantifier repetitions greedily, and when a later part of the pattern fails to match, it backtracks — undoing the most recent choice and trying the next alternative — until a match is found or all options are exhausted.
Regular Expressions & Text Parsing
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Regular Expressions & Text ParsingFlashcards8 cards
What is the core difference between a REST endpoint and a GraphQL endpoint?1 / 8
REST exposes many URLs, each returning a fixed shape of data for one resource. GraphQL exposes a single endpoint backed by a typed schema, and the client's query specifies exactly which fields it wants across related types in one request — fixing both over-fetching (unused fields) and under-fetching (needing several round trips to assemble a view).
GraphQL API Design
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GraphQL API DesignFlashcards8 cards
What is the key difference between a message queue and a pub/sub topic?1 / 8
A queue delivers each message to exactly one consumer among a competing group (work distribution). A pub/sub topic delivers a copy of each message to every subscriber (fan-out/broadcast). Many real systems (Kafka, SNS+SQS) combine both: a topic fans out to several queues, each queue load-balanced across its own consumer group.
Message Queues & Event-Driven Communication
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Message Queues & Event-Driven CommunicationFlashcards10 cards
What is the average-case time complexity of a hash map lookup?1 / 10
O(1) — a good hash function distributes keys uniformly across buckets. Worst case is O(n) when many keys collide into one bucket.
Software · L4 · DS&A — Core Structures
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Software · L4 · DS&A — Core StructuresFlashcards10 cards
What is a JIT compiler and how does V8 use it?1 / 10
A Just-In-Time compiler compiles JS to native machine code at runtime (not ahead of time). V8 initially interprets with Ignition (the bytecode interpreter), then identifies 'hot' functions and compiles them to optimized native code with TurboFan. This gives JS near-native performance on hot paths.
Engine Internals
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Engine InternalsFlashcards10 cards
What is a Web Worker and what can it NOT do?1 / 10
A Web Worker runs JS in a background thread, keeping the main thread free. It CANNOT access the DOM, window, or main-thread variables directly. Communication is via `postMessage`/`onmessage` with structured-clone data copying.
Concurrency & Advanced Patterns
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Concurrency & Advanced PatternsFlashcards10 cards
What does `strict: true` enable in tsconfig?1 / 10
It enables a suite of strict checks: `strictNullChecks`, `strictFunctionTypes`, `strictBindCallApply`, `strictPropertyInitialization`, `noImplicitAny`, `noImplicitThis`, `alwaysStrict`. Strongly recommended.
Compiler & Config
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Compiler & ConfigFlashcards10 cards
What is a branded type and how do you create one?1 / 10
A branded (nominal) type uses an intersection with a phantom tag to prevent accidental substitution of structurally identical types: `type UserId = string & { readonly _brand: 'UserId' }`. Only created via a factory, not assignable from plain string.
Advanced Patterns
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Advanced Patterns