Is this a video course?

No. This is an interactive, slide-based learning platform. Each lesson has rich text, animated diagrams, live code editors, and quizzes. You learn by reading, interacting, and doing, not by watching videos passively.

How long do I have access?

Forever. Both pricing tiers are one-time payments with lifetime access. This includes all current 766 lessons and any future content we add.

What level of experience do I need?

None. We start from absolute basics like 'What is latency?' and build up to distributed consensus protocols. The Foundation level assumes zero prior knowledge of system design.

How much does the system design course cost?

7.99 US dollars for lifetime access globally, or 499 Indian rupees for lifetime access in India. One-time payment, no subscription, no hidden fees. 11 lessons are free with no signup required.

What technologies are covered?

Everything from DNS and load balancers to Kubernetes, Kafka, distributed databases, consensus protocols, stream processing, security architecture, and observability. We cover principles and real-world implementations used at Netflix, Google, Amazon, Uber, Stripe, and more.

Is this useful for system design interview preparation?

Yes. The lessons are structured around the exact topics asked in system design interviews at FAANG and top-tier companies. Interactive diagrams help you practice whiteboard-style explanations. Covers everything from URL shortener design to distributed payment systems.

How is this different from ByteByteGo or Educative?

766 interactive lessons (4x more than most competitors), 16 different diagram types that build step by step, real production examples from Netflix, Google, Amazon, Uber, and Stripe, and lifetime access for a one-time payment of $7.99 instead of annual subscriptions costing 100 to 200 dollars per year.

Why is true exactly-once DELIVERY impossible in distributed systems?

Because the acknowledgment can be lost, making it impossible for the sender to know if the message was processed, and retrying creates a potential duplicate, The fundamental problem: the sender can't distinguish 'message processed, ACK lost' from 'message never received.' In both cases, the sender gets no ACK and must retry. But retrying when the message was already processed creates a duplicate. No protocol can solve this ambiguity at the network level.

How does Kafka achieve exactly-once PROCESSING?

By combining idempotent producers (deduplicate writes), transactional processing (atomic read-process-write-commit), and consumer-side deduplication for external effects, Kafka's exactly-once is a layered approach: idempotent producers prevent duplicate writes to the log, transactions make read-process-write-commit atomic, and for external side effects, consumer-side deduplication catches re-delivered messages. Together, these make duplicates invisible to the application.

Your system sends emails when an order is placed. Can Kafka transactions guarantee the email is sent exactly once?

No, external side effects like sending emails are outside the transaction boundary. You need idempotency at the email layer (e.g., check if the email was already sent before sending)., Kafka transactions only provide exactly-once within Kafka (topic-to-topic). Sending an email is an external side effect outside the transaction boundary. If the consumer sends the email and crashes before committing the offset, the redelivered message will trigger another email. You need application-level deduplication, check a 'sent emails' table before sending.

When is 'at-least-once with idempotent consumers' a better choice than full exactly-once transactions?

When throughput matters, the operations can easily be made idempotent, and the 10-30% performance cost of transactions isn't justified, Exactly-once transactions add significant overhead (10-30% throughput reduction in Kafka). For most systems, at-least-once delivery with idempotent consumers achieves the same result, no observable duplicates, with simpler code and better performance. Reserve full transactions for cases where idempotency is impractical.

Exactly-Once Delivery

Name: System Design Masterclass
Availability: InStock

in Messaging Event Systems

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