4 modules · 15 lessons

Core Concepts

Communication, storage, capacity, and distributed systems, explained through working examples and the tradeoffs behind them.

A network workbench connects a desktop computer, a server, and a router.
Look closely at the connections that make a system work.
Module 014 lessons

Communication and execution

  1. 01

    Request and Response

    Read HTTP contracts, reuse connections, validate inputs, and distinguish a failed response from a failed operation.

  2. 02

    DNS and CDN

    Follow name resolution and edge caching, then test cache keys, revalidation, expiry, and private responses.

  3. 03

    Load Balancers and API Gateways

    Route traffic, check backend health, drain connections, and place authentication and traffic policies at the right boundary.

  4. 04

    Parallelism and Concurrency

    Choose async tasks, threads, or processes; coordinate shared state and bound work without losing cancellation.

Module 025 lessons

Data and capacity

  1. 01

    Storage

    Choose storage by access pattern, durability, and interface, from memory and disks to databases and object stores.

  2. 02

    Numbers to Know

    Use dated hardware and AWS specifications to check CPU, memory, network, storage, and availability budgets.

  3. 03

    Back-of-the-Envelope Calculations

    Turn product activity into request rates, concurrent work, throughput, and storage growth with explicit assumptions.

  4. 04

    Indexes and MVCC

    Inspect query access paths, order composite indexes, and test snapshot visibility and conflicting updates.

  5. 05

    Caching

    Balance latency and freshness with cache strategies, eviction, bounded single-flight, and expiry jitter.

Module 034 lessons

Distributed work

  1. 01

    Queues and Retries

    Handle acknowledgements, duplicate work, outbox delivery, retry budgets, and poison messages.

  2. 02

    Distributed Systems and CAP

    Reason about partial failure, linearizability, and availability during a network partition.

  3. 03

    Replication

    Follow writes across replicas and examine lag, acknowledgement, failover, fencing, and recovery.

  4. 04

    Sharding

    Choose partition keys, expose skew, route requests, and move data while preserving query and write boundaries.

Module 042 lessons

Signals and retrieval

  1. 01

    Errors, Logs and Telemetry

    Connect frontend failures to backend logs, metrics, and traces while controlling cardinality and sensitive data.

  2. 02

    Tokens, Embeddings and RAG

    Count tokens, compare vectors, and build retrieval with access filters, context budgets, freshness, and evaluation.