Idempotency

Idempotency in Ansible

The principle that running a playbook repeatedly against the same hosts produces the same end state, and why purpose-built modules achieve it while raw command…

Idempotency in Distributed Systems

The property that performing the same operation multiple times produces the same result as performing it once, essential for safely retrying requests over unre…

What is a Remote Procedure Call (RPC)?

A Remote Procedure Call (RPC) is an IPC mechanism that lets a program invoke a procedure running in a different address space — typically on another machine —…

HTTP Methods Explained (GET, POST, PUT, PATCH, DELETE)

HTTP methods define the intended action on a resource: GET retrieves data safely without side effects, POST creates a resource or triggers processing, PUT repl…

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…

How Would You Design a Payment System?

A payment system is designed around an idempotent, append-only ledger where every state transition (authorize, capture, settle, refund) is recorded as an immut…

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 Distributed Counter (e.g. Like Counts)?

A distributed counter tracks a fast-changing count (like a like button) across many concurrent writers by sharding the counter into multiple sub-counters that…

How to Design an Airline Reservation System?

An airline reservation system is designed around a strongly consistent seat-inventory service that uses optimistic locking or short-lived holds to prevent doub…

How to Design a Shopping Cart Service

A shopping cart service stores per-user line items in a fast, durable key-value store keyed by cart ID, merges anonymous and logged-in carts on login, revalida…

How to Design a Thumbnail Generation Pipeline

A thumbnail generation pipeline listens for new-media events, fans out a set of resize/crop/format jobs to a worker pool that processes each size independently…

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 Polling System?

A polling system (like Slido or Mentimeter) is designed around a write-heavy vote-ingestion path decoupled from a read-heavy results path, using an append-only…

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…

How Would You Design an ETL Pipeline?

An ETL pipeline extracts data from source systems, transforms it into a clean, validated, and correctly shaped form, and loads it into a target store like a wa…

What are Distributed Transactions and How Do They Work?

A distributed transaction is a set of operations spanning multiple independent services or databases that must all succeed or all fail together, typically coor…

What is the Outbox Pattern?

The outbox pattern solves the dual-write problem by writing both a business state change and the event describing it into the same local database transaction,…

Exactly-Once vs At-Least-Once Delivery: What Is the Difference?

At-least-once delivery guarantees a message is delivered one or more times (never lost, but possibly duplicated), while exactly-once delivery guarantees a mess…

Polling vs Webhooks: When Should You Use Each?

Polling has a client repeatedly ask a server “is there anything new?” on a fixed interval, while a webhook has the server call a URL the client registered in a…

What are Idempotency Keys in APIs?

An idempotency key is a unique client-generated identifier attached to a mutating API request (like POST /payments) so that if the same request is retried afte…

Difference Between GET and POST

GET retrieves data and puts its parameters in the URL query string, making it idempotent, cacheable, and safe (no side effects), while POST submits data in the…

What Are Webhooks and How Do They Work?

A webhook is a user-defined HTTP callback where one system sends an automated POST request to a URL you configure whenever a specific event happens, letting yo…

What Is Idempotency in REST APIs?

An idempotent operation is one that produces the same server-side result no matter how many times an identical request is sent, so retrying it after a timeout…

HTTP Methods: Safe vs. Idempotent, What Is the Difference?

Safe means an HTTP method must not change server state at all, while idempotent means repeating the same request any number of times leaves the server in the s…

What is Infrastructure as Code?

Infrastructure as Code (IaC) is the practice of provisioning and managing infrastructure — servers, networks, databases, and more — through machine-readable de…

What is Ansible?

Ansible is an open-source, agentless configuration management and automation tool that connects to remote machines over SSH and applies tasks written in human-…