diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
new file mode 100644
index 0000000..212ff2e
--- /dev/null
+++ b/.github/workflows/tests.yaml
@@ -0,0 +1,27 @@
+name: 'Run tests'
+
+on:
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  run_tests:
+    name: Run Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Create venv
+        run: |
+          python3 -m venv venv
+          . ./venv/bin/activate
+          pip install -r requirements.txt
+          pip install black==23.7.0 pylint==2.17.5
+
+      - name: Run tests
+        run: |
+          set -e
+          . ./venv/bin/activate
+          black --check .
+          pylint *.py deps
diff --git a/conf.py b/conf.py
index e7bca57..59f835c 100644
--- a/conf.py
+++ b/conf.py
@@ -1,7 +1,10 @@
+""" Configuration settings """
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
 class Settings(BaseSettings):
+    """Settings class, loaded from .env or environment vars"""
+
     model_config = SettingsConfigDict(env_file=".env")
 
     arduino_cli_path: str = "arduino-cli"
@@ -15,6 +18,8 @@ class Settings(BaseSettings):
     # Code cache settings
     max_code_caches: int = 100
     code_cache_duration: int = 3600
+    # Max number of concurrent compile tasks
+    max_concurrent_tasks: int = 10
 
 
 settings = Settings()
diff --git a/deps/cache.py b/deps/cache.py
index f0e0fbc..3e3f631 100644
--- a/deps/cache.py
+++ b/deps/cache.py
@@ -1,3 +1,4 @@
+""" Code for caching compiled C++ code """
 from hashlib import md5
 
 from cachetools import TTLCache
diff --git a/deps/session.py b/deps/session.py
index fad4d8a..7e9cd94 100644
--- a/deps/session.py
+++ b/deps/session.py
@@ -1,3 +1,4 @@
+""" Manage session concurrency """
 import uuid
 from typing import Annotated
 
@@ -13,6 +14,7 @@
 def get_session_id(
     response: Response, session_id: Annotated[str | None, Cookie()] = None
 ):
+    """Generate or get a consistent session ID for an anonymous user"""
     if not session_id:
         # First time user, create a new session
         session_id = uuid.uuid4().hex
diff --git a/main.py b/main.py
index c2d5ce7..d1ccde2 100644
--- a/main.py
+++ b/main.py
@@ -1,3 +1,4 @@
+""" Leaphy compiler backend webservice """
 import asyncio
 import tempfile
 from os import path
@@ -20,6 +21,9 @@
     allow_headers=["*"],
 )
 
+# Limit compiler concurrency to prevent overloading the vm
+semaphore = asyncio.Semaphore(settings.max_concurrent_tasks)
+
 
 async def _install_libraries(libraries: list[Library]):
     # Install required libraries
@@ -46,8 +50,8 @@ async def _compile_sketch(sketch: Sketch) -> dict[str, str]:
         sketch_path = f"{dir_name}/{file_name}"
 
         # Write the sketch to a temp .ino file
-        async with aiofiles.open(sketch_path, "w+") as f:
-            await f.write(sketch.source_code)
+        async with aiofiles.open(sketch_path, "w+") as _f:
+            await _f.write(sketch.source_code)
 
         compiler = await asyncio.create_subprocess_exec(
             settings.arduino_cli_path,
@@ -64,12 +68,13 @@ async def _compile_sketch(sketch: Sketch) -> dict[str, str]:
         if compiler.returncode != 0:
             raise HTTPException(500, stderr.decode() + stdout.decode())
 
-        async with aiofiles.open(f"{sketch_path}.hex", "r") as f:
-            return {"hex": await f.read()}
+        async with aiofiles.open(f"{sketch_path}.hex", "r") as _f:
+            return {"hex": await _f.read()}
 
 
 @app.post("/compile/cpp")
 async def compile_cpp(sketch: Sketch, session_id: Session) -> dict[str, str]:
+    """Compile code and return the result in HEX format"""
     # Make sure there's no more than X compile requests per user
     sessions[session_id] += 1
 
@@ -81,9 +86,10 @@ async def compile_cpp(sketch: Sketch, session_id: Session) -> dict[str, str]:
             return compiled_code
 
         # Nope -> compile and store in cache
-        await _install_libraries(sketch.libraries)
-        result = await _compile_sketch(sketch)
-        code_cache[cache_key] = result
-        return result
+        async with semaphore:
+            await _install_libraries(sketch.libraries)
+            result = await _compile_sketch(sketch)
+            code_cache[cache_key] = result
+            return result
     finally:
         sessions[session_id] -= 1
diff --git a/models.py b/models.py
index ba91378..4403533 100644
--- a/models.py
+++ b/models.py
@@ -1,3 +1,4 @@
+""" FastAPI models """
 from typing import Annotated
 
 from pydantic import BaseModel, Field
@@ -7,7 +8,8 @@
 
 
 class Sketch(BaseModel):
+    """Model representing a arduino Sketch"""
+
     source_code: str
-    # TODO: make this an enum with supported board types
     board: str
     libraries: list[Library] = []
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..a62d1e8
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,3 @@
+[tool.pylint.'MESSAGES CONTROL']
+max-line-length = 120
+disable = "too-few-public-methods, import-error"