how to solve slippage problem

Yeah, I mostly agree with that. Slippage is just part of real market conditions, especially with scalping. On demo or even different account types, execution can feel smoother, but once you’re on a real, live server with real liquidity, small delays and price changes start to matter a lot.
You can’t really “solve” slippage, only try to reduce it a bit with better latency and avoiding crazy volatility.

also one thing to consider is that you will *always* have tighter spreads and lower slippage at the opening of a bar, because that's when all algorithmic trading setups that rely on open bar open/close orders
I made a test using MT5 and their historical spreads and I found out that my guess was right
maybe try to adapt your scalping strategy to open trades on open bars ?

also there is the fact that millions of people will trade at the *exact* same time as you.
It's not like volatility algorithms differ from EA to EA. *every* EA trades on high volatility peaks, unrelated on how they define volatility peaks
so you compete with million of people that willl trade at the exact same time as you...
obviously it will not work that way

You can’t get rid of slippages. They will always be here, and it’s totally normal. This is live trading environments, it’s not simulation. And don’t think that if you change the broker the slippages will magically disappear. In fact, the bigger the lot size you trade, the larger the slippages are. This is again normal, because in order for your position to be executed, the system in the background is looking for an exact match for the price and executed. When small size lots, it’s easier to find a match. When it’s a bigger lot size, it gets harder to find a match.
So, try trading with small lots. This thing can work.
But what works the best is to try to make your strategy resistant to small slippages.

Quite common with scalping EAs, actually.
Scalping systems are extremely sensitive to execution conditions. Even small differences between accounts can change performance. Compare trade logs from both accounts (entry price, spread, slippage) - that will usually reveal the reason.

Most likely you’re seeing the difference between demo pricing and real market execution. On live accounts, slippage is real especially with scalping EAs that rely on very small TP/SL distances. Even a 0.5–1 pip negative slip or slightly wider spread during fast ticks can completely distort the edge.
Also check execution speed, VPS latency, and whether your EA was optimized on demo conditions that didn’t include real liquidity gaps. On live servers, during volatility or low liquidity, orders may get filled at the next available price not the requested one. For scalping, that small difference is everything. You might want to forward test with a slightly wider SL/TP or add a max slippage filter to see if performance stabilizes.

There are some things you have some control over.
Instead of market orders you could use limits when opening a trade (yes you will miss trades)
Find a broker with fast execution times.
Stuff like that. Stuff you already are told about.

But there's stuff you do have control over. Your computer, network and internet.

Clean PC
Run your EA on a extremely clean PC. No virus scanners. No firewall. No adblocker. All those things interfere with your data stream. Not much, but we are talking milliseconds here.
It's not just about turning them off. Not having installed them at all.
Risk of infection? Well never use your trading PC for anything besides your trading software.

Network
The latency of a WiFi connection is about 10x higher that a wired connection.
This might be even worse when you are in a crowded area. (yes neighbors have influence on your WiFi performance).
LAN (wired) latency is 1-5ms. WiFi 10-50ms and above.
To simplify it, that's the time for your order to travel from your PC to your modem.

Internet type
Fiber has the lowest latency.
Please note that latency is not the same than download or upload speed. Trading doesn't require an 8Gbit line.
This part is about how long it takes from your modem to travel to a data center.


Other things
Then there's the whole route from the data center to your broker.
You can control this is only two ways.
Move and live close to your broker's server.
Or get a VPS that's close to your broker's server. Ideal would be a VPS is the same data center as your broker.

If your EA is fully automatic, a VPS solves most of the things I mentioned.

Pick a good broker. Some brokers got caught by first trying to match trades among their own clients only, and then route them to the market.
That way they could pocket all the spreads. The trader often got a sub-optimal price. If routed to the market, time has passed.

In short here is a paradox, if you want scalper ea to work perfectly you need to find Market Maker Broker ( BBOOk) not an ABOOK.

Veterans know the story with XMT scalper, its doing awesome on backtests, and sometimes demo, in real account conditions its a disaster. Only time it worked was when i found a bbook broker who didnt reroute my orders to Liquidity Provider. By going through Bbbook i saved 100-200 ms on execution. But as soon as e was profitable, broker would simply dump orders to LP, and switch me though ABook and i would get slippage because it would take more time for order to get executed. Nothing illegal here its just how the game works.

I only trade XAUUSD, and its impossible to solve slippage problem, unless your broker use B book