Interactive Tools

Learn by playing,
not just reading.

Premium simulators & developer utilities — right in the browser, nothing to install. Eight tools below, all live, all offline.

Base64 Encoder / Decoder

Live · UTF-8 safe · runs entirely in your browser

JWT Decoder

Live · header + payload decoded locally · nothing leaves your browser

Header
—
Payload
—
Signature
—
Simulators

The concepts that are hard to picture

Every widget runs live in your browser — no accounts, no network, no install.

Rate Limiter Visualizer

Live · token bucket vs leaky bucket, animated

Algorithm
Capacity
10
Refill / sec
4/s
Allowed
0
Dropped (429)
0
Tokens
10

Consistent Hashing Ring

Live · add/remove nodes, watch which keys move

Virtual nodes / server
12
Sample keys
60
Nodes
3
Keys moved (last change)
—
Modulo would move
—

Consistent hashing remaps only about 1/N of keys when a server joins or leaves — the highlighted dots. Plain hash % N reshuffles almost everything. More virtual nodes = smoother, more even distribution.

Cache Eviction Simulator

Live · LRU vs LFU vs FIFO on one request stream

Policy (visualized)
Cache size
4
Cache slots
Hits
0
Misses
0
Hit rate
—

Same stream, all three policies scored side by side. LRU evicts the least-recently used, LFU the least-frequently used, FIFO the oldest inserted — regardless of use.

Redis Memory Calculator

Live · estimate RAM for N keys, types & TTLs

Number of keys
Value type
Avg value size (bytes)
Expiry
Estimated dataset
—
Per key
—
Peak RSS (~1.5×)
—

API Latency / Tail Calculator

Live · Monte-Carlo p50 & p99 for a chain of hops

End-to-end p50
—
End-to-end p99
—
p99.9
—

Cron Expression Explainer

Live · plain English + the next 5 run times

Meaning
—
Next 5 runs