diff --git a/.circleci/config.yml b/.circleci/config.yml
index 46e2166e..2920bc7e 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -1,94 +1,182 @@
-version: 2
+version: 2.1
+
+orbs:
+   win: circleci/windows@1.0.0
+
 workflows:
-  version: 2
   test:
     jobs:
-      - test-2.7
-      - test-3.3
-      - test-3.4
-      - test-3.5
-      - test-3.6
-      - test-3.7
-test-template: &test-template
-  steps:
-    - checkout
-    - run:
-        name: install requirements
-        command: |
-          sudo pip install --upgrade pip virtualenv;
-          sudo pip install -r test-requirements.txt;
-          if [[ "$CIRCLE_JOB" != "test-3.3" ]]; then
-            sudo pip install -r test-filesource-optional-requirements.txt;
-          fi;
-          if [[ "$CIRCLE_JOB" != "test-3.3" ]] && [[ "$CIRCLE_JOB" != "test-3.4" ]]; then
-            sudo pip install -r consul-requirements.txt;
-          fi;
-          sudo python setup.py install;
-          pip freeze
-    - run:
-        name: run tests
-        command: |
-          mkdir test-reports;
-          if [[ "$CIRCLE_JOB" == "test-2.7" ]]; then
-            pytest -s --cov=ldclient --junitxml=test-reports/junit.xml testing;
-            sh -c '[ -n "${CODECLIMATE_REPO_TOKEN+1}" ] && codeclimate-test-reporter || echo "No CODECLIMATE_REPO_TOKEN value is set; not publishing coverage report"';
-          else
-            pytest -s --junitxml=test-reports/junit.xml testing;
-          fi
-    - run:
-        name: test packaging/install
-        # Note, virtualenv isn't supported on Python 3.3 and this test requires virtualenv. But we
-        # never build our published package on 3.3 anyway.
-        command: |
-          if [[ "$CIRCLE_JOB" != "test-3.3" ]]; then
-            sudo rm -rf dist *.egg-info;
-            ./test-packaging/test-packaging.sh;
-          fi
-    - store_test_results:
-        path: test-reports
-    - store_artifacts:
-        path: test-reports
+      - test-linux:
+          name: Python 2.7
+          docker-image: circleci/python:2.7-jessie
+          test-with-codeclimate: true  # we only need to run CodeClimate in one job
+      - test-linux:
+          name: Python 3.3
+          docker-image: circleci/python:3.3-jessie
+          consul-supported: false  # Consul isn't supported in 3.3
+          filesource-supported: false  # FileDataSource isn't supported in 3.3
+          test-packaging: false  # packaging test requires virtualenv, which isn't supported in 3.3
+      - test-linux:
+          name: Python 3.4
+          docker-image: circleci/python:3.4-jessie
+          consul-supported: false  # Consul isn't supported in 3.4
+      - test-linux:
+          name: Python 3.5
+          docker-image: circleci/python:3.5-jessie
+      - test-linux:
+          name: Python 3.6
+          docker-image: circleci/python:3.6-jessie
+      - test-linux:
+          name: Python 3.7
+          docker-image: circleci/python:3.7-stretch
+      - test-linux:
+          name: Python 3.8
+          docker-image: circleci/python:3.8-buster
+      - test-windows:
+          name: Windows Py2.7
+          py3: false
+      - test-windows:
+          name: Windows Py3.3
+          py3: true
 
 jobs:
-  test-2.7:
-    <<: *test-template
+  test-linux:
+    parameters:
+      docker-image:
+        type: string
+      consul-supported:
+        type: boolean
+        default: true
+      filesource-supported:
+        type: boolean
+        default: true
+      test-packaging:
+        type: boolean
+        default: true
+      test-with-codeclimate:
+        type: boolean
+        default: false
     docker:
-      - image: circleci/python:2.7-jessie
-      - image: redis
-      - image: amazon/dynamodb-local
-      - image: consul
-  test-3.3:
-    <<: *test-template
-    docker:
-      - image: circleci/python:3.3-jessie
-      - image: redis
-      - image: amazon/dynamodb-local
-      # python-consul doesn't support Python 3.3
-  test-3.4:
-    <<: *test-template
-    docker:
-      - image: circleci/python:3.4-jessie
-      - image: redis
-      - image: amazon/dynamodb-local
-      # python-consul doesn't support Python 3.4
-  test-3.5:
-    <<: *test-template
-    docker:
-      - image: circleci/python:3.5-jessie
-      - image: redis
-      - image: amazon/dynamodb-local
-      - image: consul
-  test-3.6:
-    <<: *test-template
-    docker:
-      - image: circleci/python:3.6-jessie
-      - image: redis
-      - image: amazon/dynamodb-local
-      - image: consul
-  test-3.7:
-    <<: *test-template
-    docker:
-      - image: circleci/python:3.7-stretch
+      - image: <<parameters.docker-image>>
       - image: redis
       - image: amazon/dynamodb-local
       - image: consul
+    steps:
+      - checkout
+      - run:
+          name: install requirements
+          command: |
+            sudo pip install --upgrade pip virtualenv;
+            sudo pip install -r test-requirements.txt;
+            if [[ "<<parameters.filesource-supported>>" == "true" ]]; then
+              sudo pip install -r test-filesource-optional-requirements.txt;
+            fi;
+            if [[ "<<parameters.consul-supported>>" == "true" ]]; then
+              sudo pip install -r consul-requirements.txt;
+            fi;
+            sudo python setup.py install;
+            pip freeze
+      - when:
+          condition: <<parameters.test-with-codeclimate>>
+          steps:
+            - run:
+                name: run tests (with CodeClimate)
+                command: |
+                  mkdir test-reports
+                  pytest -s --cov=ldclient --junitxml=test-reports/junit.xml testing -W error::SyntaxWarning
+                  sh -c '[ -n "${CODECLIMATE_REPO_TOKEN+1}" ] && codeclimate-test-reporter || echo "No CODECLIMATE_REPO_TOKEN value is set; not publishing coverage report"'
+      - unless:
+          condition: <<parameters.test-with-codeclimate>>
+          steps:
+            - run:
+                name: run tests
+                command: |
+                  mkdir test-reports
+                  pytest -s --junitxml=test-reports/junit.xml testing -W error::SyntaxWarning
+      - when:
+          condition: <<parameters.test-packaging>>
+          steps:
+            - run:
+                name: test packaging/install
+                command: |
+                  sudo rm -rf dist *.egg-info
+                  ./test-packaging/test-packaging.sh
+      - store_test_results:
+          path: test-reports
+      - store_artifacts:
+          path: test-reports
+
+  test-windows:
+    executor:
+      name: win/vs2019
+      shell: powershell.exe
+    parameters:
+      py3:
+        type: boolean
+    steps:
+      - checkout
+      - when:
+          condition: <<parameters.py3>>
+          steps:
+            - run:
+                name: install Python 3
+                command: choco install python --no-progress
+      - unless:
+          condition: <<parameters.py3>>
+          steps:
+            - run:
+                name: install Python 2.7
+                command: |
+                  $ProgressPreference = "SilentlyContinue"  # prevents console errors from CircleCI host
+                  iwr -outf python-2.7.16.amd64.msi https://www.python.org/ftp/python/2.7.16/python-2.7.16.amd64.msi
+                  Start-Process msiexec.exe -Wait -ArgumentList '/I python-2.7.16.amd64.msi /quiet'
+      - run:
+          name: set up DynamoDB
+          command: |
+            $ProgressPreference = "SilentlyContinue"
+            iwr -outf dynamo.zip https://s3-us-west-2.amazonaws.com/dynamodb-local/dynamodb_local_latest.zip
+            mkdir dynamo
+            Expand-Archive -Path dynamo.zip -DestinationPath dynamo
+            cd dynamo
+            javaw -D"java.library.path=./DynamoDBLocal_lib" -jar DynamoDBLocal.jar
+          background: true
+      - run:
+          name: set up Consul
+          command: |
+            $ProgressPreference = "SilentlyContinue"
+            iwr -outf consul.zip https://releases.hashicorp.com/consul/1.4.2/consul_1.4.2_windows_amd64.zip
+            mkdir consul
+            Expand-Archive -Path consul.zip -DestinationPath consul
+            cd consul
+            sc.exe create "Consul" binPath="$(Get-Location)/consul.exe agent -dev"
+            sc.exe start "Consul"
+      - run:
+          name: start Redis
+          command: |
+            $ProgressPreference = "SilentlyContinue"
+            iwr -outf redis.zip https://github.com/MicrosoftArchive/redis/releases/download/win-3.0.504/Redis-x64-3.0.504.zip
+            mkdir redis
+            Expand-Archive -Path redis.zip -DestinationPath redis
+            cd redis
+            ./redis-server --service-install
+            ./redis-server --service-start
+            Start-Sleep -s 5
+            ./redis-cli ping
+      - run:
+          name: install requirements
+          command: |
+            $env:Path += ";C:\Python27\;C:\Python27\Scripts\"  # has no effect if 2.7 isn't installed
+            python --version
+            pip install -r test-requirements.txt
+            pip install -r consul-requirements.txt
+            python setup.py install
+      - run:
+          name: run tests (2.7)
+          command: |
+            mkdir test-reports
+            $env:Path += ";C:\Python27\;C:\Python27\Scripts\"  # has no effect if 2.7 isn't installed
+            python -m pytest -s --junitxml=test-reports/junit.xml testing;
+      - store_test_results:
+          path: test-reports
+      - store_artifacts:
+          path: test-reports
diff --git a/azure-pipelines.yml b/azure-pipelines.yml
deleted file mode 100644
index af1f3342..00000000
--- a/azure-pipelines.yml
+++ /dev/null
@@ -1,84 +0,0 @@
-jobs:
-  - job: build
-    pool:
-      vmImage: 'vs2017-win2016'
-    steps:
-      - task: PowerShell@2
-        displayName: 'Setup Dynamo'
-        inputs:
-          targetType: inline
-          workingDirectory: $(System.DefaultWorkingDirectory)
-          script: |
-            iwr -outf dynamo.zip https://s3-us-west-2.amazonaws.com/dynamodb-local/dynamodb_local_latest.zip
-            mkdir dynamo
-            Expand-Archive -Path dynamo.zip -DestinationPath dynamo
-            cd dynamo
-            javaw -D"java.library.path=./DynamoDBLocal_lib" -jar DynamoDBLocal.jar
-      - task: PowerShell@2
-        displayName: 'Setup Consul'
-        inputs:
-          targetType: inline
-          workingDirectory: $(System.DefaultWorkingDirectory)
-          script: |
-            iwr -outf consul.zip https://releases.hashicorp.com/consul/1.4.2/consul_1.4.2_windows_amd64.zip
-            mkdir consul
-            Expand-Archive -Path consul.zip -DestinationPath consul
-            cd consul
-            sc.exe create "Consul" binPath="$(System.DefaultWorkingDirectory)/consul/consul.exe agent -dev"
-            sc.exe start "Consul"
-      - task: PowerShell@2
-        displayName: 'Setup Redis'
-        inputs:
-          targetType: inline
-          workingDirectory: $(System.DefaultWorkingDirectory)
-          script: |
-            iwr -outf redis.zip https://github.com/MicrosoftArchive/redis/releases/download/win-3.0.504/Redis-x64-3.0.504.zip
-            mkdir redis
-            Expand-Archive -Path redis.zip -DestinationPath redis
-            cd redis
-            ./redis-server --service-install
-            ./redis-server --service-start
-      - task: UsePythonVersion@0
-        inputs:
-          versionSpec: '2.7'
-          addToPath: true
-      - task: PowerShell@2
-        displayName: 'Setup SDK and Test 2.7'
-        inputs:
-          targetType: inline
-          workingDirectory: $(System.DefaultWorkingDirectory)
-          script: |
-            python --version
-            pip install -r test-requirements.txt
-            pip install -r consul-requirements.txt
-            python setup.py install
-            mkdir test-reports27
-            python -m pytest -s --junitxml=test-reports27/junit.xml testing;
-      - task: UsePythonVersion@0
-        inputs:
-          versionSpec: '3.7'
-          addToPath: true
-      - task: PowerShell@2
-        displayName: 'Setup SDK and Test 3.7'
-        inputs:
-          targetType: inline
-          workingDirectory: $(System.DefaultWorkingDirectory)
-          script: |
-            python --version
-            pip install -r test-requirements.txt
-            pip install -r consul-requirements.txt
-            python setup.py install
-            mkdir test-reports37
-            python -m pytest -s --junitxml=test-reports37/junit.xml testing;
-      - task: CopyFiles@2
-        inputs:
-          targetFolder: $(Build.ArtifactStagingDirectory)/test-reports27
-          sourceFolder: $(System.DefaultWorkingDirectory)/test-reports27
-      - task: CopyFiles@2
-        inputs:
-          targetFolder: $(Build.ArtifactStagingDirectory)/test-reports37
-          sourceFolder: $(System.DefaultWorkingDirectory)/test-reports37
-      - task: PublishBuildArtifacts@1
-        inputs:
-          pathtoPublish: '$(Build.ArtifactStagingDirectory)'
-          artifactName: reports
diff --git a/requirements.txt b/requirements.txt
index 2e3cba6f..f941d6ab 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 backoff>=1.4.3
 certifi>=2018.4.16
-expiringdict>=1.1.4
+expiringdict>=1.1.4,<1.2.0
 six>=1.10.0
 pyRFC3339>=1.0
 semver>=2.7.9
diff --git a/testing/__init__.py b/testing/__init__.py
index d2b1b498..0602017d 100644
--- a/testing/__init__.py
+++ b/testing/__init__.py
@@ -1,3 +1,6 @@
+import logging
 import os
 
+logging.basicConfig(level=logging.WARN)
+
 sdk_key = os.environ.get('LD_SDK_KEY')
diff --git a/testing/test_init.py b/testing/test_init.py
index 16d67b6c..ca13c130 100644
--- a/testing/test_init.py
+++ b/testing/test_init.py
@@ -3,7 +3,6 @@
 import ldclient
 from ldclient import Config
 
-logging.basicConfig(level=logging.DEBUG)
 mylogger = logging.getLogger()