Maximum Lot size beyond which it is difficult to open or close a trade?

I’m trading in micro lots.
I usually place market orders.
They can be opened and closed instantly.

I want to know…
What is the maximum lot size beyond which it is difficult to open or close an order?

Does it vary from broker to broker?
Is it different for different currency pairs?
What about limit orders and stop orders?
The time of the day, day of the week and forex sessions?

If you use your maximum lot and then the market moves against your order; then instantly you’ll face your MC; in this case leverage is an important parameter!

By Maximum lot size I didn’t mean maximum lot size allowed for my account in its current state.

What I meant was… the maximum lot size in general beyond which it gets difficult to open or close the trade depending on the volume and liquidity available at my broker or FX Market.
I’m wondering if it’s a really big lot size then it might take some time to completely fill my order. Or perhaps a hell lot of time.
Pardon me if my assumption is wrong. I’m new to Forex.

That is depending on broker, but you can easily assume 1000 lots.