Database connection pooling

<div class="demo"><div class="head"><b>CONNECTION POOL</b><span>2 slots</span></div><div class="stage pool"><div class="requests"><div class="pill">req A</div><div class="pill">req B</div><div class="pill" id="reqC">req C</div></div><div class="poolarrow">→</div><div class="slots"><div class="cell" id="slotA">conn 1 · A</div><div class="cell" id="slotB">conn 2 · B</div></div></div><div class="foot"><span id="poolstatus">C waits for a slot</span><span>borrow → return</span></div></div>

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let n=0;function tick(){document.getElementById('reqC').classList.toggle('on',!!n);document.getElementById('slotA').textContent=n?'conn 1 · C':'conn 1 · A';document.getElementById('slotA').classList.toggle('on',!!n);document.getElementById('poolstatus').textContent=n?'A returns · C borrows':'C waits for a slot';n=1-n}tick();const t=setInterval(tick,1200);document.querySelector('.demo').onclick=()=>{clearInterval(t);tick()}