Performance issues with large codebases

I'm facing massive performance issues with a project that I'm working on which contains a lot of files. In this codebase completion is nearly unusable, causes lots of Lua & out of memory errors & crashes the native LSP.

One of the very common errors I get is this

Error executing luv callback:
...ovim/HEAD-7ba28b1/share/nvim/runtime/lua/vim/lsp/rpc.lua:558: cannot resume dead coroutine
Press ENTER or type command to continue

To make sure this was not the native LSP itself, I did the following:

• Removed all the plugins
• Installed all of them including nvim-lspconfig but without completion-nvim
• Tested (with omni-completion setlocal omnifunc=v:lua.vim.lsp.omnifunc) -> everything ran very smoothly & fast
• Installed completion-nvim
• Tested -> performance issues all over the place (editor is locked, completion takes a lot of time, etc…)

I tried to see if coc.nvim has the same issues or no & I tried that & it worked fine too.

This is my completion.nvim config & this is my LSP config

Note, the same exact LSP config works fine without completion.nvim which also means that the TypeScript LSP is not the culprit too.