Reliability

Hadoop Best Practices

A practical guide to designing, tuning, and operating Hadoop clusters so they stay reliable and performant as data volumes grow.

How to Answer "How Do You Handle Repetitive Tasks?"

The strongest answer shows you stay reliable and consistent on repetitive work while actively looking for ways to automate, streamline, or improve the process,…

When Should You Use TCP vs UDP?

Use TCP when correctness and ordered, complete delivery matter more than latency (web pages, file transfers, APIs), and use UDP when low latency and minimal ov…

What is a Message Queue?

A message queue is a middleware component that lets a producer publish messages which sit durably in a buffer until a consumer pulls and processes them, decoup…

What is Rate Limiting?

Rate limiting is the practice of capping how many requests a client can make to a service within a given time window, protecting the system from overload and a…

What is Idempotency in System Design?

Idempotency means that performing the same operation multiple times produces the same result as performing it once, so retries or duplicate requests do not cau…

What is a Single Point of Failure (SPOF)?

A single point of failure (SPOF) is any component in a system whose failure alone causes the entire system, or a critical part of it, to become unavailable, an…

How to Design a Rate Limiter?

A rate limiter is designed by choosing an algorithm (token bucket, leaky bucket, fixed window, or sliding window log) that tracks request counts per client key…

How Would You Design a Notification System?

A notification system is designed as an event-driven pipeline where upstream services publish notification events to a queue, a set of channel-specific workers…

How to Design a Distributed Message Queue

A distributed message queue is designed as partitioned, append-only logs replicated across brokers, where producers write to a partition by key, consumers in a…

How Would You Design a Distributed Lock?

A distributed lock is a coordination primitive that lets multiple independent processes across different machines agree that only one of them may hold a named…

How to Design an API Rate Limiter

An API rate limiter design centers on a shared, low-latency counter store (typically Redis) that tracks per-client request counts using a sliding-window or tok…

How Would You Design a Feature Flag System?

A feature flag system decouples code deployment from feature release by storing flag state in a fast, centrally managed store that services poll or subscribe t…

How Would You Design a Distributed Job Scheduler?

A distributed scheduler is a system that reliably triggers jobs at the right time across a fleet of worker nodes, using a durable job store, a leader-elected t…

How Would You Design a Large-Scale Email Delivery Service?

A large-scale email service accepts send requests via an API, queues them for asynchronous delivery, routes through multiple outbound relays with reputation ma…

How to Design a Distributed Job Queue

A distributed job queue accepts jobs from producers, persists them durably with priority and visibility-timeout semantics, and hands them out to a pool of work…

How to Design a Distributed Cron Scheduler

A distributed cron scheduler stores job definitions with their schedule in a durable database, uses a leader-elected or lock-based trigger process to fire each…

How to Design a Group Chat System

A group chat system stores each group's membership and messages durably, fans out new messages to every online member's connection via a messaging service, and…

What is the Thundering Herd Problem?

The thundering herd problem occurs when a large number of processes or requests are all woken up or triggered simultaneously by the same event — such as a popu…

What is Backpressure in Distributed Systems?

Backpressure is a flow-control mechanism where a slower downstream consumer signals an upstream producer to slow down or pause sending data, preventing the con…

What is the Circuit Breaker Pattern?

The circuit breaker pattern wraps a call to a remote dependency with a state machine that stops sending requests to a service once it detects repeated failures…

What is the Bulkhead Pattern?

The bulkhead pattern isolates resources such as thread pools, connection pools, or processes per dependency or workload so that a failure or slowdown in one pa…

What is Retry with Exponential Backoff?

Retry with exponential backoff is a strategy for re-attempting a failed request after progressively longer wait times between each retry, often with added rand…

What is a Dead Letter Queue?

A dead letter queue (DLQ) is a separate holding queue where messages are routed after they repeatedly fail to be processed successfully, so a poison message ca…

What are Sticky Sessions in Load Balancing?

Sticky sessions (session affinity) are a load balancer configuration that routes all requests from a given client to the same backend server for the duration o…