diff --git a/infra/docker/Dockerfile.backend b/infra/docker/Dockerfile.backend
index e832c08..79ca8f8 100644
--- a/infra/docker/Dockerfile.backend
+++ b/infra/docker/Dockerfile.backend
@@ -1,4 +1,4 @@
-FROM node:22-slim
+FROM node:22-alpine
 
 WORKDIR /app
 
@@ -6,10 +6,11 @@ WORKDIR /app
 RUN npm install -g pnpm
 
 # Install build tools for native dependencies (node-crc, @discordjs/opus)
-RUN apt-get update -qq && apt-get install -y -qq --no-install-recommends python3 make g++ wget && rm -rf /var/lib/apt/lists/*
+# @discordjs/voice is a shared workspace dependency needed even by backend
+RUN apk add --no-cache python3 make g++
 
 # Create non-root user
-RUN groupadd --system app && useradd --system -g app app
+RUN addgroup -S app && adduser -S -G app app
 
 # Copy dependency definition files first for better caching
 COPY pnpm-workspace.yaml .
diff --git a/infra/docker/Dockerfile.discord-gateway b/infra/docker/Dockerfile.discord-gateway
index e89ef9f..8167c41 100644
--- a/infra/docker/Dockerfile.discord-gateway
+++ b/infra/docker/Dockerfile.discord-gateway
@@ -11,10 +11,7 @@ RUN addgroup -S app && adduser -S -G app app
 # Install build tools for native dependencies (node-crc, @discordjs/opus)
 # and ffmpeg for voice transmit (PCM to OggOpus encoding)
 # This is done early to cache this expensive layer
-RUN apk add --no-cache python3 make g++ rust cargo ffmpeg linux-headers
-
-# Use bundled node headers for native addon compilation
-ENV npm_config_nodedir=/usr/local
+RUN apk add --no-cache python3 make g++ rust cargo ffmpeg
 
 # Copy dependency definition files first for better caching
 COPY pnpm-workspace.yaml .