Explainers

Every ViLearn explainer, each one a visual story with a live simulation and a knowledge check, and the Ask ViLearn tutor beside all three.

Networking

How the internet finds google.comDNS · Name resolution · Caching and TTLs — Beginner · 8 min
How two strangers agree they can hear each otherTCP · Three-way handshake · Packet loss and retries — Beginner · 9 min
Why the video you are about to watch is already in your cityCDNs · Edge caching · ISP peering — Intermediate · 12 min
How two strangers get a secret past everyone in the roomTLS · HTTPS · Certificates — Intermediate · 10 min
How a service decides who gets inRate limiting · Token bucket · 429 Too Many Requests — Beginner · 9 min
Why a chat message arrives instantly, and what holding the line costsWebSockets · Polling · Real-time messaging — Intermediate · 11 min

Who restarts your app at 3 A.M.?Deployment · Reconciliation loops · Process supervision — Beginner · 9 min
How Kubernetes keeps your app aliveKubernetes · Containers · Self-healing clusters — Beginner · 9 min
Why your dashboard was green while users were leavingObservability · Percentiles and p99 · Alerting — Intermediate · 10 min
Scaling the summitHorizontal scaling · Load balancing · Stateless services — Intermediate · 11 min
Why your service never made the call it thinks it madeService mesh · Sidecar proxy · Istio — Intermediate · 11 min

How Elasticsearch finds your needle in a billion documentsElasticsearch · Inverted index · Full-text search — Intermediate · 12 min
How a database finds one row in a millionDatabase indexes · B-trees · Query planning — Intermediate · 11 min
The list that only says noBloom filters · Probabilistic data structures · False positives — Intermediate · 10 min
Why two correct transfers can lose moneyDatabase transactions · Isolation levels · Lost update — Intermediate · 9 min

Why the agent's edit failed on a file it read correctlyAI coding agents · File edits · Exact string matching — Intermediate · 12 min
Why a coding agent forgets everything between stepsAI agents · Tool calling · The agent loop — Intermediate · 12 min
How Git actually stores your workGit · Content-addressed objects · Branches and HEAD — Intermediate · 10 min

Why changing one number in the URL still worksAuthorization · IDOR · Access control — Beginner · 8 min

Why sending the model more can make the answer worseContext windows · Prompt engineering · Lost in the middle — Intermediate · 9 min
How gradient descent makes machines learnGradient descent · Neural network training · Learning rate — Intermediate · 10 min
How mixture of experts makes giant models affordableMixture of experts · Sparse models · Token routing — Advanced · 11 min
How an LLM picks the next wordLLMs · Attention · Tokens and sampling — Advanced · 12 min

The secret lives of deleted filesFilesystems · Inodes · Deletion and recovery — Beginner · 9 min
Jury duty for serversConsensus · Raft · Leader election — Advanced · 12 min
Why a log beats a queue when two teams want the same eventKafka · Event logs · Consumer offsets — Intermediate · 11 min
The multitasking illusionCPU scheduling · Context switching · Concurrency vs parallelism — Beginner · 9 min
How a cluster decides which server holds your dataConsistent hashing · Sharding · Rebalancing — Intermediate · 10 min
How your operating system fakes an entire computerOperating systems · Interrupts · Virtual memory — Intermediate · 11 min
What a queue really does when you are overloadedQueueing · Backpressure · Latency under load — Intermediate · 10 min
Why a road turns red without anyone counting a carGoogle Maps traffic · GPS probe data · Map matching — Intermediate · 11 min
Why one expired key takes down a database that was 20% busyCaching · Cache stampede · Retry storms — Advanced · 11 min
Why the ride you get is not the nearest carGeospatial indexing · Real-time matching · Dispatch — Advanced · 12 min