Largest ring size ever used in a Monero transacation

Question

What is the largest ring size ever used in a Monero transaction?

What was the size of that transaction in kB?

Please share the transaction ID if available

Answer 1

According to Monero Blocks statistics the highest pre RingCT ringsize was 850. I was not able to immediately locate that transaction on the blockchain.

I was able to find a sample 150 mixin transaction from block 1,067,631 with a size of 70,219 bytes and a transaction fee of 0.69 XMR.

The above pre RingCT ring size and transaction size records were prior to the introduction of RingCT. With the recent v0.10.3.1 point release a new dynamic block size limiter algorithm was introduced to account for the unexpectedly fast adoption of RingCT.

Someone recently completed a transaction with a new record ringsize of 4500 with a size of 306,775 bytes and tx fee of 0.093729000000 XMR. This transaction appears to be near current limits, with anything larger according to smooth likely being:

too big relative to fee and penalty (unless the block size grows). If it were slightly smaller, say 4000 instead of 5000, it likely would confirm and with a fee of less than $2. That's a pretty nice demo of how to achieve an extreme degree of untracability at significant but not obscene cost.