diff --git a/.travis.yml b/.travis.yml
index b0d2a02ad..5a74935fa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,7 +22,7 @@ matrix:
   include:
     - os: linux
       env:
-        - PYTHON=3.6
+        - PYTHON=3.6 SMALL_AND_LARGE_TESTS=1
         - PYTHONWARNINGS=ignore
         - RAY_DEFAULT_BUILD=1
         - RAY_CYTHON_EXAMPLES=1
@@ -32,6 +32,36 @@ matrix:
       before_script:
         - . ./ci/travis/ci.sh build
 
+    - os: linux
+      env:
+        - PYTHON=3.6 MEDIUM_TESTS_A_TO_J=1
+        - PYTHONWARNINGS=ignore
+        - RAY_DEFAULT_BUILD=1
+        - RAY_CYTHON_EXAMPLES=1
+        - RAY_USE_RANDOM_PORTS=1
+      install:
+        - . ./ci/travis/ci.sh init RAY_CI_SERVE_AFFECTED,RAY_CI_TUNE_AFFECTED,RAY_CI_PYTHON_AFFECTED
+      before_script:
+        - . ./ci/travis/ci.sh build
+      script:
+        # bazel python tests for medium size tests. Used for parallelization.
+        - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only,medium_size_python_tests_a_to_j python/ray/tests/...; fi
+
+    - os: linux
+      env:
+        - PYTHON=3.6 MEDIUM_TESTS_K_TO_Z=1
+        - PYTHONWARNINGS=ignore
+        - RAY_DEFAULT_BUILD=1
+        - RAY_CYTHON_EXAMPLES=1
+        - RAY_USE_RANDOM_PORTS=1
+      install:
+        - . ./ci/travis/ci.sh init RAY_CI_SERVE_AFFECTED,RAY_CI_TUNE_AFFECTED,RAY_CI_PYTHON_AFFECTED
+      before_script:
+        - . ./ci/travis/ci.sh build
+      script:
+        # bazel python tests for medium size tests. Used for parallelization.
+        - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only,medium_size_python_tests_k_to_z python/ray/tests/...; fi
+
     - os: linux
       env:
         - PYTHON=3.6 BAZEL_CONFIG="asan"
@@ -48,7 +78,7 @@ matrix:
     - os: osx
       osx_image: xcode7
       env:
-        - PYTHON=3.6
+        - PYTHON=3.6 SMALL_AND_LARGE_TESTS=1
         - PYTHONWARNINGS=ignore
         - RAY_DEFAULT_BUILD=1
         - RAY_CYTHON_EXAMPLES=1
@@ -58,6 +88,38 @@ matrix:
       before_script:
         - . ./ci/travis/ci.sh build
 
+    - os: osx
+      osx_image: xcode7
+      env:
+        - PYTHON=3.6 MEDIUM_TESTS_A_TO_J=1
+        - PYTHONWARNINGS=ignore
+        - RAY_DEFAULT_BUILD=1
+        - RAY_CYTHON_EXAMPLES=1
+        - RAY_USE_RANDOM_PORTS=1
+      install:
+        - . ./ci/travis/ci.sh init RAY_CI_SERVE_AFFECTED,RAY_CI_TUNE_AFFECTED,RAY_CI_PYTHON_AFFECTED
+      before_script:
+        - . ./ci/travis/ci.sh build
+      script:
+        # bazel python tests for medium size tests. Used for parallelization.
+        - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only,medium_size_python_tests_a_to_j python/ray/tests/...; fi
+
+    - os: osx
+      osx_image: xcode7
+      env:
+        - PYTHON=3.6 MEDIUM_TESTS_K_TO_Z=1
+        - PYTHONWARNINGS=ignore
+        - RAY_DEFAULT_BUILD=1
+        - RAY_CYTHON_EXAMPLES=1
+        - RAY_USE_RANDOM_PORTS=1
+      install:
+        - . ./ci/travis/ci.sh init RAY_CI_SERVE_AFFECTED,RAY_CI_TUNE_AFFECTED,RAY_CI_PYTHON_AFFECTED
+      before_script:
+        - . ./ci/travis/ci.sh build
+      script:
+        # bazel python tests for medium size tests. Used for parallelization.
+        - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only,medium_size_python_tests_k_to_z python/ray/tests/...; fi
+
     - os: linux
       env:
         - JDK='Oracle JDK 8'
@@ -360,7 +422,7 @@ script:
   - (cd deploy/ray-operator && export CC=gcc && suppress_output go build && suppress_output go test ./...)
 
   # bazel python tests. This should be run last to keep its logs at the end of travis logs.
-  - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only python/ray/tests/...; fi
+  - if [ $RAY_CI_PYTHON_AFFECTED == "1" ]; then ./ci/keep_alive bazel test --config=ci $(./scripts/bazel_export_options) --test_tag_filters=-jenkins_only,-medium_size_python_tests_a_to_j,-medium_size_python_tests_k_to_z python/ray/tests/...; fi
   # NO MORE TESTS BELOW, keep them above.
 
 after_script:
diff --git a/python/ray/tests/BUILD b/python/ray/tests/BUILD
index 5f1ee4e51..a597e2e44 100644
--- a/python/ray/tests/BUILD
+++ b/python/ray/tests/BUILD
@@ -31,6 +31,15 @@ py_test_module_list(
     "test_global_gc.py",
     "test_iter.py",
     "test_joblib.py",
+  ],
+  size = "medium",
+  extra_srcs = SRCS,
+  tags = ["exclusive", "medium_size_python_tests_a_to_j"],
+  deps = ["//:ray_lib"],
+)
+
+py_test_module_list(
+  files = [
     "test_memory_limits.py",
     "test_memory_scheduling.py",
     "test_metrics.py",
@@ -54,7 +63,7 @@ py_test_module_list(
   ],
   size = "medium",
   extra_srcs = SRCS,
-  tags = ["exclusive"],
+  tags = ["exclusive", "medium_size_python_tests_k_to_z"],
   deps = ["//:ray_lib"],
 )