diff --git a/denops/ddc/base/source.ts b/denops/ddc/base/source.ts
index cce54fa..25dd596 100644
--- a/denops/ddc/base/source.ts
+++ b/denops/ddc/base/source.ts
@@ -10,7 +10,7 @@ import type {
   Previewer,
   SourceOptions,
 } from "../types.ts";
-import { convertKeywordPattern } from "../utils.ts";
+import { convertKeywordPattern, getKeywordRegExp } from "../utils.ts";
 
 import type { Denops } from "@denops/std";
 
@@ -106,7 +106,7 @@ export abstract class BaseSource<
     );
 
     const completePos = args.context.input.search(
-      new RegExp("(?:" + keywordPattern + ")$"),
+      getKeywordRegExp("(?:" + keywordPattern + ")$"),
     );
     return completePos;
   }
diff --git a/denops/ddc/ddc.ts b/denops/ddc/ddc.ts
index f468bbf..e3086e6 100644
--- a/denops/ddc/ddc.ts
+++ b/denops/ddc/ddc.ts
@@ -31,7 +31,7 @@ import type { Denops } from "@denops/std";
 import * as autocmd from "@denops/std/autocmd";
 import * as op from "@denops/std/option";
 import * as fn from "@denops/std/function";
-import { batch } from "@denops/std/batch";
+import { batch, collect } from "@denops/std/batch";
 
 import { assertEquals } from "@std/assert/equals";
 
@@ -622,9 +622,12 @@ export class Ddc {
       return;
     }
 
-    const input = denops.call("ddc#util#get_input", context.event);
-    const mode = fn.mode(denops);
-    if (context.input !== await input || context.mode !== await mode) {
+    const [currentInput, currentMode] = await collect(denops, (denops) => [
+      // ddc#util#get_input always returns a string; cast for type inference.
+      denops.call("ddc#util#get_input", context.event) as Promise<string>,
+      fn.mode(denops),
+    ]);
+    if (context.input !== currentInput || context.mode !== currentMode) {
       // Input is changed.  Skip invalid completion.
       await this.hide(denops, context, options);
       return;
diff --git a/denops/ddc/ext.ts b/denops/ddc/ext.ts
index 9e34f7c..9ee6f73 100644
--- a/denops/ddc/ext.ts
+++ b/denops/ddc/ext.ts
@@ -237,14 +237,11 @@ export async function filterItems(
     userFilters: UserFilter[],
     items: Item[],
   ): Promise<Item[]> {
+    const resolvedList = await Promise.all(
+      userFilters.map((uf) => getFilter(denops, loader, options, uf)),
+    );
     const resolved: ResolvedFilter[] = [];
-    for (const userFilter of userFilters) {
-      const [filter, filterOptions, filterParams] = await getFilter(
-        denops,
-        loader,
-        options,
-        userFilter,
-      );
+    for (const [filter, filterOptions, filterParams] of resolvedList) {
       if (!filter) {
         return [];
       }
diff --git a/denops/ddc/utils.ts b/denops/ddc/utils.ts
index be266dc..1c49ddd 100644
--- a/denops/ddc/utils.ts
+++ b/denops/ddc/utils.ts
@@ -15,6 +15,12 @@ import { fromFileUrl } from "@std/path/from-file-url";
 import { join } from "@std/path/join";
 import { dirname } from "@std/path/dirname";
 
+// Cache size limit: in practice only a handful of distinct keywordPattern /
+// iskeyword combinations appear, so 64 entries is more than enough.
+const KEYWORD_CACHE_MAX = 64;
+const convertKeywordPatternCache = new Map<string, string>();
+const keywordRegExpCache = new Map<string, RegExp>();
+
 export async function convertKeywordPattern(
   denops: Denops,
   keywordPattern: string,
@@ -23,13 +29,37 @@ export async function convertKeywordPattern(
   const iskeyword = bufnr === undefined
     ? await op.iskeyword.getLocal(denops)
     : await op.iskeyword.getBuffer(denops, bufnr);
+  // Neither iskeyword nor keywordPattern contain NUL bytes, so this
+  // composite key is unambiguous.
+  const cacheKey = keywordPattern + "\0" + iskeyword;
+  const cached = convertKeywordPatternCache.get(cacheKey);
+  if (cached !== undefined) {
+    return cached;
+  }
   const keyword = vimoption2ts(iskeyword);
   const replaced = keywordPattern
     .replaceAll("\\k", "[" + keyword + "]")
     .replaceAll("[:keyword:]", keyword);
+  if (convertKeywordPatternCache.size >= KEYWORD_CACHE_MAX) {
+    convertKeywordPatternCache.clear();
+  }
+  convertKeywordPatternCache.set(cacheKey, replaced);
   return replaced;
 }
 
+export function getKeywordRegExp(expandedPattern: string): RegExp {
+  const cached = keywordRegExpCache.get(expandedPattern);
+  if (cached !== undefined) {
+    return cached;
+  }
+  const re = new RegExp(expandedPattern);
+  if (keywordRegExpCache.size >= KEYWORD_CACHE_MAX) {
+    keywordRegExpCache.clear();
+  }
+  keywordRegExpCache.set(expandedPattern, re);
+  return re;
+}
+
 // See https://github.com/vim-denops/denops.vim/issues/358 for details
 export function isDenoCacheIssueError(e: unknown): boolean {
   const expects = [