diff --git a/dockerfiles/ruby-3.3.Dockerfile b/dockerfiles/ruby-3.3.Dockerfile
index 37ff3fbf..26a9d8a2 100644
--- a/dockerfiles/ruby-3.3.Dockerfile
+++ b/dockerfiles/ruby-3.3.Dockerfile
@@ -1,7 +1,22 @@
+# syntax=docker/dockerfile:1.7-labs
 FROM ruby:3.3-alpine
 
+# Required for installing the json/async gems
+RUN apk add --no-cache \
+    build-base=0.5-r3 \
+    libssl3=3.3.1-r3 \
+    readline-dev=8.2.10-r0 \
+    zlib-dev=1.3.1-r1
+
+# Re-build if Gemfile or Gemfile.lock changes
 ENV CODECRAFTERS_DEPENDENCY_FILE_PATHS="Gemfile,Gemfile.lock"
+
 WORKDIR /app
 
-COPY Gemfile Gemfile.lock ./
-RUN bundle install --verbose
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+# .git & README.md are unique per-repository. We ignore them on first copy to prevent cache misses
+COPY --exclude=.git --exclude=README.md . /app
+
+RUN bundle install --verbose
+
+# Once the heavy steps are done, we can copy all files back
+COPY . /app
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