Achievements Optimizer Mod (26.1.2, 1.20.1) – Reduces Server Lag

Achievements Optimizer Mod is a lightweight performance mod that optimizes how item-based achievements and advancements are processed – reducing unnecessary inventory scans and improving overall tick efficiency. It doesn’t change any gameplay mechanics or logic – only makes achievement checks faster and cleaner under the hood.

Features:

Key Optimizations

• Early tick skipping – heavy slot calculations (empty/occupied/full) are skipped early, preventing extra work per event.
• Instant empty stack discard – with ignoreEmptyStacks enabled, empty stacks are removed immediately without scanning the entire inventory.
• Fast multi-item matching – single-pass inventory check using boolean[] flags with early exit. No allocations, noticeably faster on large inventories or long condition lists.
• Early slot filtering – slots.matches(full, empty, occupied) is evaluated first, avoiding deeper checks when slots don’t match.
• Preserved fast path for single targets – when items.size() == 1, the comparison is done directly on the changed slot without a full inventory pass.

Result

• Fewer redundant checks, less memory churn, and faster responses to inventory events.
• Particularly beneficial for servers or modpacks with many players and complex advancement triggers.

Screenshots:

Achievements Optimizer Mod Download Links