Seventy
tools for the
working engineer.
Everything runs in your browser. Paste, inspect, format, decode. Pair any tool with a guide that explains what is actually happening underneath.
Start with a guide.
All guides →The TLS handshake
How two machines come to agree upon a secret.
DNS, how names resolve
From your resolver all the way out to the root.
The TCP handshake
SYN, SYN-ACK, ACK — and what each bit is for.
WebSockets
Full-duplex over HTTP — upgrade, frames, keepalive.
HTTP caching
Where each layer — browser, CDN, app, database — earns its keep.
CDN anatomy
PoPs, anycast, cache keys, origin shielding.
OAuth 2, the flows
Authorization code, PKCE, client credentials — when each one fits.
OpenID Connect
Identity on top of OAuth — the ID token, claims, discovery.
Database indexing
B-tree, hash, and covering indexes — picked apart.
Write-ahead logging
Why every durable store writes the log first.
ACID transactions
The four letters, the four isolation levels, and the anomalies each permits.
Garbage collection
Mark-and-sweep, generational, concurrent — without the fog.
Memory allocation
Stacks, heaps, arenas, and why fragmentation matters.
Event loops
Single-threaded concurrency — queues, microtasks, I/O.
Thread pools
Work-stealing, bounded queues, backpressure.
Go channels
Buffered, unbuffered, select — CSP in practice.
Hash tables
Open addressing vs chaining, resize, load factor.
Ring buffers
Wait-free queues for one producer and one consumer.
Kafka, as a river
Topics, partitions, and why offsets — not timestamps — are the truth.
Redis internals
Single-threaded, in-memory, durable when it has to be.
Message queues
Push, pull, fan-out, dead-letter. A practical taxonomy.
Realtime communication
Polling, SSE, WebSockets, WebRTC — when each fits.
API gateways
Routing, auth, rate limits, and where they belong.
Reverse proxies
Nginx, Envoy, HAProxy — what they actually do.
Load balancing
Layer 4 vs 7, algorithms, health checks, session affinity.
Autoscaling
Horizontal, vertical, cluster — and the metrics that drive each.
Service discovery
DNS, registries, meshes — how services find services.
Containers
Namespaces, cgroups, OCI — what a container really is.
Kubernetes pod creation
From kubectl apply to a running container, with every hop named.
K8s networking
Pod network, Services, CNI, Ingress — the layers explained.
VPC networking
Subnets, route tables, NAT gateways, transit.
NAT traversal
Why peer-to-peer is hard and how STUN/TURN help.
BGP, the glue
Internet routing between autonomous systems — in plain prose.
Distributed IDs
UUID, ULID, Snowflake, Sonyflake — which for which.
Max-flow
Ford–Fulkerson, augmenting paths, min-cut.
Graph routing
Dijkstra, A*, Bellman–Ford — when each is right.
Git, from the inside
Blobs, trees, commits — the DAG that powers everything.
The Internet, a journey
The seven phases that carry a packet from browser to origin.
Toolkit is built for engineers and students who want to see a system work, not just read about it. Each tool is paired, where possible, with a guide — and each guide with a simulator you can actually push on. It is fast because it is simple: no build step between you and the answer.