I didn't see this in real time, but only found this when reviewing my screen recorder and looking at the milli-seconds.
Full disclosure, I found this while reviewing the Lightspeed Demo.
Last Friday, 8/20/21, monthly options expiration day.
I saw lots of suspicious activity, but will only share one in this thread.
I've suspected option front-running, but what I saw, looked like an extreme example of it.
This happened at 15:53 NYC time.
(Time stamp is from my screen recorder that sees milliseconds. Lightspeed doesn't show milliseconds.)
These three screenshots happened in about 20 milliseconds.
444 PUT is 1xITM 445 PUT is 2xITM
Below is timestamp, 0.43 seconds (43milliseconds)

0.53 seconds (53 milliseconds)

1.00 seconds (100 milliseconds)

-----------------------------------------------------------------------------------------
Time and Sales is showing a 200 contract execution at the 53millisecond time stamp, for 0.59. There is enough liquidity here to fill a 200 order all the way down MPRL @ 1.48.
To reach .59, I totaled 673 contracts need to be transacted 1st.

However, it seems >50% of all Bids disappeared when the order showed up to fill them at .59, instead of 1.51, 1.49, and 1.48
I want to repeat, there's only 20 milliseconds between all 3 images.
20 milliseconds!

Oddly, the L2 didn't reflect the book change until 10 milliseconds later.
Perhaps that's just a demo thing?
Perhaps that's just lag with Lightspeeds data provider?
Just ignoring that lag, doesn't this look highly suspicious?
This looks like illegal front running to me.
I seems the person entered a Market order to either exit a trade or open a short and suddenly the market disappeared and they filled at 61% worse price.
Full disclosure, I found this while reviewing the Lightspeed Demo.
Last Friday, 8/20/21, monthly options expiration day.
I saw lots of suspicious activity, but will only share one in this thread.
I've suspected option front-running, but what I saw, looked like an extreme example of it.
This happened at 15:53 NYC time.
(Time stamp is from my screen recorder that sees milliseconds. Lightspeed doesn't show milliseconds.)
These three screenshots happened in about 20 milliseconds.
444 PUT is 1xITM 445 PUT is 2xITM
Below is timestamp, 0.43 seconds (43milliseconds)

0.53 seconds (53 milliseconds)

1.00 seconds (100 milliseconds)

-----------------------------------------------------------------------------------------
Time and Sales is showing a 200 contract execution at the 53millisecond time stamp, for 0.59. There is enough liquidity here to fill a 200 order all the way down MPRL @ 1.48.
To reach .59, I totaled 673 contracts need to be transacted 1st.

However, it seems >50% of all Bids disappeared when the order showed up to fill them at .59, instead of 1.51, 1.49, and 1.48
I want to repeat, there's only 20 milliseconds between all 3 images.
20 milliseconds!

Oddly, the L2 didn't reflect the book change until 10 milliseconds later.
Perhaps that's just a demo thing?
Perhaps that's just lag with Lightspeeds data provider?
Just ignoring that lag, doesn't this look highly suspicious?
This looks like illegal front running to me.
I seems the person entered a Market order to either exit a trade or open a short and suddenly the market disappeared and they filled at 61% worse price.
)
