Ravnary · an open library
Clear explanations, practice that checks you, and review that brings it back, organised by subject.
Huginn carries the thought out. Muninn brings it back.
Picked for October
Four System Design topics that take a single box to a system that holds up under load.
Load balancers, reverse proxies and API gateways: the three kinds of server that sit in front of yours, and the one job each is for.
Why start hereEvery later topic in this set assumes you can tell the three apart.
Beginner to Intermediate10 cards · 5 q
Caching: keeping copies of frequent reads close, deciding when they go stale, and the ways a cache can take a system down.
Beginner to Advanced9 cards · 8 qnot started
Scaling a web system up or out: bigger machines or more of them, what has to be stateless first, and what autoscaling cannot catch.
Beginner to Advanced9 cards · 5 qnot started
Message queues and publish/subscribe: handing work off without waiting, and choosing between one reader and many.
Beginner to Intermediate9 cards · 6 qnot started
Each one is short, stands on its own, and ends with a quiz.
A path tells you what to read next, even when the next step is in another subject.
The order to learn Java in, from a file that compiles to code that runs on more than one thread.
The order to learn Spring in, from what the container does to a REST service backed by real data.
The order to learn data structures and algorithms in, from counting what code costs to solving a coding problem never seen before.
Collection
The path that builds the ground, the patterns interviewers reach for, and one page to revise from the night before.
1 path · 2 topics · 1 cheatsheet
Fourteen coding interview patterns on one page: the property that points to each, what it costs, when it fails, and its loop in Python.
Arrays and numbers
The order to learn data structures and algorithms in, from counting what code costs to solving a coding problem never seen before.
Sliding window: keeping a running answer for a contiguous run as it slides, with a fixed size or one that grows and shrinks, and the inputs that break it.
Intermediate to Advanced8 cards · 5 qnot started
Fast and slow pointers: two pointers moving at different speeds that find a list's middle, detect a cycle and locate where the cycle starts.
Intermediate to Advanced8 cards · 4 qnot started
One page each, grouped to be scanned in a minute and printed on A4.
Every everyday Java collection on one page: what each one is for, what it costs, and how to choose.
Lists
Every data structure in the subject on one page: what each one is for, what its operations cost, and how to choose.
Sequences
Traversal, ordering, shortest paths, spanning trees and connectivity on one page: which algorithm a graph question needs and what it costs.
Traversal
Each one stands on its own, needs nothing read before it, and ends with a quiz.
Reading UML class diagrams: the boxes, lines and arrowheads every design pattern is drawn with, and how each relationship looks in code.
Beginner to Intermediate8 cards · 5 qnot started
Back-of-the-envelope estimation: turning users and their actions into requests a second, storage and downtime, before choosing a single part.
Beginner to Intermediate8 cards · 6 qnot started
API pagination with offsets and cursors: returning large results a page at a time without skipping rows or slowing down.
Beginner to Intermediate8 cards · 5 qnot started
Three to begin with. The rest are on the Learn page.
Running software in containers, and building images that other people can run.
Designing HTTP APIs that clients can understand, call safely, and keep using as the API changes.
Following a request from an application down through the network layers and back, and naming the layer where a network problem lives.
The whole library
Every subject sits in a field and its categories. Start from the field you work in, or the one you want to learn next.
7 fields · 22 categories