Throughout different versions, I play and build on a world that uses command blocks and optimized fashion according to how the performance can be within the various versions of Minecraft Bedrock. For example, I have studied how in the version of 1.17.40, maybe even 1.17.34, I have noticed when playing multiplayer for this world becomes a lot slower when a horde of mobs are being used while I host games. Previous versions beforehand, the same number of command blocks placed, rendered under two ticking areas, I could have spawned much more mobs before the arrival of "server lag."

Approximation Using Two Ticking Areas Using Command Blocks :

Before 1.17.40 - Mobs Available to Spawn: ~50-75 Mobs (Mob Spawning Always Off)
After 1.17.40 - Mobs Available to Spawn: ~20 or Fewer Mobs (20 is a rare occasion)

Approximate Command Blocks Active For One Ticking Area: ~100-120 Command Blocks (LABELED: "UE" | For Particles and Executed Effects of either different weapons or perk system [1])
Second Active Area: (LABELED: "main" | For general system, used for progression, games, and perks activity across all various games and content) ~70-80 Command Blocks

All of these are approximations and not actual data for what is being used. Counting will occur soon in actuality and will be labeled here below:

Accurate Count of Command Blocks Active For One Ticking Area: UNKNOWN (LABELED: "UE" | For Particles and Executed Effects of either different weapons or perk system [1])
Second Active Area: (LABELED: "main" | For general system, used for progression, games, and perks activity across all various games and content) UNKNOWN

Mobs are harder to detect since they require an active player to help estimate a base for what will lag and what will not, dependent on the scenario so that the approximation will remain.

Over time, I have learned to optimize more with the game's progression and how different things will work in the future. However, I cannot undermine how each version progressively makes server performance and optimization worse over time, considering that block entities are wholly broken in rendering/simulating. That includes command blocks and structure blocks (when loading or saving structures, do not use command blocks to save/load them either, still causes significant lag issues), including client-based rendering, which puts more considerable pressure on the server.

You can try replicating this by having a world or a new flat world, where it'll run more freely but continuously adding more command blocks, using either detection-based execution commands (/execute + /execute, testfor, etc.). If you want, you can add particle-based execution commands for entities or even sound playing variants. You can get creative however you like.

Try getting the number to what is being approximately used from different areas, and then try seeing it yourself by placing other mobs together.

Expected Result:

Mobs should match previous versions' performance simulation against the server and client and add more people to get more severe results. Version counts from 1.17.34 or less. Minor occurrence happens before 1.17 in their entirety.

Observed Result:

Throughout never versions, the server starts to slow down more often. However, it may not show in solo but happens much more quickly with multiplayer. It progressively worsens over time, especially with one active tick area, where it's approximately ~2-2.5x more mobs than in the general approximation labeled above.

My friend and I, who have done matches together, can confirm that the game was fine and continuous until (# of mobs spawned before 1.17.40 approx.) were spawned, which was fine and a minor inconvenience. But, now, it started to become more of a problem in his latest session. Exact labeled details as before above, those numbers made the server lag much more, and more added adds to the problem heavily. When using the intended commands, it starts even lagging more. It can occur with EVEN FEWER mobs, which is absurd at best.

I can give more updates over time to see what can go wrong. In another bug report, I may mention that Ghasts are utterly broken in multiplayer, being them entirely stopping the server affecting connectivity across all players and interaction with the world.

I hope this does not get a "DUPLICATE" since this is not client-based, where it affects FPS, more so in line with the world itself and how everything is being simulated. So far, I do not see other tickets making this claim when searching for similar topics.