Ledger LandISSUE #3 of 90

distributed systems · cap theorem refresher

BlockyVSDouble-Spend Dan

Blocky saysBlockchain is a distributed system — and inherits the CAP-theorem trade-offs of all of them.

Many machines holding copies must stay consistent — the classic distributed-systems challenge. CAP says under a network partition you can't have both perfect consistency and full availability. Blockchains lean toward consistency and partition-tolerance, accepting latency (confirmation times) and eventual finality. Understanding this explains why transactions aren't instant and why "more confirmations = safer".

Power-ups you unlock

Many nodes must agree on one state
CAP: trade consistency vs availability under partition
Blockchains favor consistency + partition tolerance
Hence latency and "wait for confirmations"

Double-Spend Dan attacks — common mistakes

Expecting instant, final transactions
Ignoring network/partition realities
Assuming all chains make the same CAP trade-off

Boss battleExplain why "wait for N confirmations" exists in CAP terms.

Example code

<!doctype html><html><head><meta charset="utf-8"></head>
<body style="background:#06040d;color:#e6e0ff;font-family:monospace;padding:20px"><pre>CAP: pick 2 under partition
blockchain → consistency + partition tolerance
→ confirmations add finality over time</pre></body></html>

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