System Design
81 bites tagged System Design — interview questions with model answers, and 60-second explainers.
Design a system correlating CI/CD deployments with observability metrics
Tests event-driven correlation and temporal join patterns across distributed data. Strong answers outline: async deploy event ingestion, time-windowed metric joins with version tags, and handling clock skew.
Design column-level data lineage from source to dashboard
Propose AST extractors for Spark and dbt, a graph DB for column edges, and an API for impact analysis. Metadata architecture tracing columns through heterogeneous batch and SQL engines.
Design a real-time mobile analytics pipeline
Tests decoupling high-volume ingestion from low-latency querying. Strong designs use an event broker, a stream processor for windowed aggregates, and an OLAP database for sub-second dashboards.
Describe data architecture for fast multi-dimensional slicing and pre-computation trade-offs
Tests analytical architecture trade-offs between latency and cost. Strong answers propose a hybrid pipeline: columnar warehouse for flexible exploration plus pre-aggregated OLAP cubes for sub-second dashboards.
Design a client-side event batching system for a high-traffic app
This tests your grasp of frontend performance and data reliability. Outline a batching strategy (timer/size), then explain using `visibilitychange` with `navigator.sendBeacon()` to prevent data loss on unload. A red flag is suggesting synchronous XHR.
E2E Testing: The Final Check, Not The Whole Strategy
E2E testing is a dress rehearsal for your app, simulating a full user journey. Use it sparingly for critical flows like checkout, as it tests all services together. The footgun is over-reliance: they are slow, brittle, and hard to debug.
Node.js Child Processes: Escaping the Main Thread
A child process lets your Node.js app run external commands without blocking the event loop. Use it for CPU-intensive tasks like image processing or running system utilities. The footgun: using synchronous versions (`execSync`) will block your entire server.
Resource Exhaustion: Starving a System to Death
A resource exhaustion attack is a denial-of-service tactic that starves a system by consuming all of a finite resource like CPU or database connections. It exploits missing rate limits or quotas.
Webhooks: Don't Call Us, We'll Call You
A webhook is an automated HTTP callback from a service to your app when an event happens. Instead of polling for updates, the service calls you. This is how Stripe signals a payment or GitHub a commit.
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