diff --git a/src/js/game/components/belt.js b/src/js/game/components/belt.js
index d98db49a..a9be5c99 100644
--- a/src/js/game/components/belt.js
+++ b/src/js/game/components/belt.js
@@ -5,6 +5,7 @@ import { BaseItem } from "../base_item";
 import { Vector, enumDirection } from "../../core/vector";
 import { Math_PI, Math_sin, Math_cos } from "../../core/builtins";
 import { globalConfig } from "../../core/config";
+import { Entity } from "../entity";
 
 export class BeltComponent extends Component {
     static getId() {
@@ -12,6 +13,7 @@ export class BeltComponent extends Component {
     }
 
     static getSchema() {
+        // The followUpCache field is not serialized.
         return {
             direction: types.string,
             sortedItems: types.array(types.pair(types.float, types.obj(gItemRegistry))),
@@ -34,6 +36,9 @@ export class BeltComponent extends Component {
 
         /** @type {Array<[number, BaseItem]>} */
         this.sortedItems = [];
+
+        /** @type {Entity} */
+        this.followUpCache = null;
     }
 
     /**
diff --git a/src/js/game/systems/belt.js b/src/js/game/systems/belt.js
index 5fa5a265..a4b6d85f 100644
--- a/src/js/game/systems/belt.js
+++ b/src/js/game/systems/belt.js
@@ -13,14 +13,13 @@ import { MetaBeltBaseBuilding } from "../buildings/belt_base";
 import { defaultBuildingVariant } from "../meta_building";
 import { GameRoot } from "../root";
 import { createLogger } from "../../core/logging";
+import { Rectangle } from "../../core/rectangle";
 
 const BELT_ANIM_COUNT = 6;
 const SQRT_2 = Math_sqrt(2);
 
 const logger = createLogger("belt");
 
-/** @typedef {Array<{ entity: Entity, followUp: Entity }>} BeltCache */
-
 export class BeltSystem extends GameSystemWithFilter {
     constructor(root) {
         super(root, [BeltComponent]);
@@ -66,9 +65,8 @@ export class BeltSystem extends GameSystemWithFilter {
         this.root.signals.entityDestroyed.add(this.updateSurroundingBeltPlacement, this);
 
         this.cacheNeedsUpdate = true;
-
-        /** @type {BeltCache} */
-        this.beltCache = [];
+        /** @type {Rectangle[]} */
+        this.smallUpdateAreas = [];
     }
 
     /**
@@ -119,6 +117,12 @@ export class BeltSystem extends GameSystemWithFilter {
                 }
             }
         }
+
+        // Optimize for the common case of adding or removing buildings one at a time.
+        // Clicking and dragging can fire up to 4 create/destroy signals.
+        if (this.cacheNeedsUpdate) {
+            this.smallUpdateAreas.push(affectedArea.expandedInAllDirections(1));
+        }
     }
 
     draw(parameters) {
@@ -163,42 +167,28 @@ export class BeltSystem extends GameSystemWithFilter {
         return null;
     }
 
-    /**
-     * Adds a single entity to the cache
-     * @param {Entity} entity
-     * @param {BeltCache} cache
-     * @param {Set} visited
-     */
-    computeSingleBeltCache(entity, cache, visited) {
-        // Check for double visit
-        if (visited.has(entity.uid)) {
-            return;
-        }
-        visited.add(entity.uid);
-
-        const followUp = this.findFollowUpEntity(entity);
-        if (followUp) {
-            // Process followup first
-            this.computeSingleBeltCache(followUp, cache, visited);
-        }
-
-        cache.push({ entity, followUp });
-    }
-
     computeBeltCache() {
         logger.log("Updating belt cache");
 
-        let cache = [];
-        let visited = new Set();
-        for (let i = 0; i < this.allEntities.length; ++i) {
-            this.computeSingleBeltCache(this.allEntities[i], cache, visited);
+        if (this.smallUpdateAreas.length <= 4) {
+            for (let i = 0; i < this.smallUpdateAreas.length; ++i) {
+                const area = this.smallUpdateAreas[i];
+                for (let x = area.x; x < area.right(); ++x) {
+                    for (let y = area.y; y < area.bottom(); ++y) {
+                        const tile = this.root.map.getTileContentXY(x, y);
+                        if (tile && tile.components.Belt) {
+                            tile.components.Belt.followUpCache = this.findFollowUpEntity(tile);
+                        }
+                    }
+                }
+            }
+        } else {
+            for (let i = 0; i < this.allEntities.length; ++i) {
+                const entity = this.allEntities[i];
+                entity.components.Belt.followUpCache = this.findFollowUpEntity(entity);
+            }
         }
-        assert(
-            cache.length === this.allEntities.length,
-            "Belt cache mismatch: Has " + cache.length + " entries but should have " + this.allEntities.length
-        );
-
-        this.beltCache = cache;
+        this.smallUpdateAreas = [];
     }
 
     update() {
@@ -217,8 +207,8 @@ export class BeltSystem extends GameSystemWithFilter {
             beltSpeed *= 100;
         }
 
-        for (let i = 0; i < this.beltCache.length; ++i) {
-            const { entity, followUp } = this.beltCache[i];
+        for (let i = 0; i < this.allEntities.length; ++i) {
+            const entity = this.allEntities[i];
 
             const beltComp = entity.components.Belt;
             const items = beltComp.sortedItems;
@@ -244,8 +234,8 @@ export class BeltSystem extends GameSystemWithFilter {
                 maxProgress = 1 - globalConfig.itemSpacingOnBelts;
             } else {
                 // Otherwise our progress depends on the follow up
-                if (followUp) {
-                    const spacingOnBelt = followUp.components.Belt.getDistanceToFirstItemCenter();
+                if (beltComp.followUpCache) {
+                    const spacingOnBelt = beltComp.followUpCache.components.Belt.getDistanceToFirstItemCenter();
                     maxProgress = Math.min(2, 1 - globalConfig.itemSpacingOnBelts + spacingOnBelt);
 
                     // Useful check, but hurts performance
@@ -270,8 +260,8 @@ export class BeltSystem extends GameSystemWithFilter {
                 progressAndItem[0] = Math.min(maxProgress, progressAndItem[0] + speedMultiplier * beltSpeed);
 
                 if (progressAndItem[0] >= 1.0) {
-                    if (followUp) {
-                        const followUpBelt = followUp.components.Belt;
+                    if (beltComp.followUpCache) {
+                        const followUpBelt = beltComp.followUpCache.components.Belt;
                         if (followUpBelt.canAcceptItem()) {
                             followUpBelt.takeItem(progressAndItem[1], progressAndItem[0] - 1.0);
                             items.splice(itemIndex, 1);