Visualizers
Learn by moving things
Interactive explainers for the ideas behind retrieval, embeddings, and agents. A formula tells you what is true; dragging a vector shows you why. Each one also appears inside the article it belongs to, and runs entirely in your browser, so drag, poke, and break it.
At-least-once: keep trying until you hear back
From: Delivery Guarantees: At-Least-Once, Exactly-Once, and Idempotency →The sender retries until it gets an acknowledgment, so a message is never lost. But if the acknowledgment itself is lost, it resends and the receiver gets a duplicate: a card charged twice. Never lost, sometimes doubled.
The sender sends the message and waits for an acknowledgment.
Idempotency: a key so a repeat changes nothing
From: Delivery Guarantees: At-Least-Once, Exactly-Once, and Idempotency →Each request carries a unique idempotency key. The first delivery charges the card and records the key; a retry with the same key is recognized and skipped. Delivered twice, charged once: exactly-once in practice, the Stripe pattern.
The sender attaches a unique idempotency key, a1b2, to the charge.
Ordering: same messages, wrong order, wrong answer
From: Delivery Guarantees: At-Least-Once, Exactly-Once, and Idempotency →Deposit 100 then withdraw 50 on an account that cannot go negative ends at 50. Reorder the two and the withdrawal is rejected against a zero balance, ending at 100: the same messages, a different answer. Keeping them in order prevents it.
Two events for one account that starts at 0 and may not go negative: deposit 100, then withdraw 50.