Function invoke_unchecked 

pub unsafe fn invoke_unchecked(
    instruction: &InstructionView<'_, '_, '_, '_>,
    accounts: &[CpiAccount<'_>],
) -> ProgramResult

Invoke a CPI without borrow validation (lowest CU cost).

This is Tier C of the CPI surface. The checked variant (invoke) enforces the full contract below before calling this function; prefer that unless you have measured a reason to bypass the validation pass.

Safety

The caller must uphold every one of the following invariants. A violation of any of them is undefined behaviour, because the Solana runtime’s sol_invoke_signed_c syscall assumes they already hold.

1. No aliasing borrows. No & or &mut references into any account data region referenced by accounts may be live for the duration of the call. The CPI can (and will) mutate those regions via the callee, and Rust’s aliasing rules do not permit the caller to hold outstanding references to memory that is about to change under it.
2. Account list consistency. Every CpiAccount in accounts must correspond to a real account previously passed to the program’s entrypoint (same address, same is_signer / is_writable flags the runtime already knows about). The runtime will not re-derive account permissions; invalid flags propagate into the callee.
3. Writability coverage. Every account that the instruction marks writable must have is_writable = true in accounts, and every account the instruction marks as signer must have is_signer = true. Mismatches are rejected by the runtime but the rejection path is not cheap and the caller is expected to get this right.
4. No shared mutable slices across CPIs. If the same account appears more than once in accounts (duplicate accounts), the caller is responsible for ensuring that any subsequent borrow of that account’s data respects the CPI’s writes.
5. Valid instruction encoding. instruction.program_id, instruction.accounts, and instruction.data must all point to valid memory for the duration of the call. An InstructionView built from a local InstructionAccount slice is fine; one built from a dropped stack slot is not.

The runtime does not enforce any of these from the caller side — it assumes a well-formed CPI. That is the cost of the Tier C path.