diff --git a/app/main.py b/app/main.py
index 3f30a21..dda7100 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1,3 +1,117 @@
-from app.api import create_app
+from contextlib import asynccontextmanager
+from datetime import UTC, datetime
+from typing import Annotated, AsyncIterator
+from uuid import UUID
 
-app = create_app()
+from fastapi import Depends, FastAPI, HTTPException, Response, status
+
+from app.checker import EndpointChecker
+from app.config import get_settings
+from app.logging import configure_logging
+from app.models import CurrentStatus, Monitor, MonitorCreate, MonitorUpdate, State
+from app.security import DestinationRejected
+from app.store import MonitorStore
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI) -> AsyncIterator[None]:
+    settings = get_settings()
+    configure_logging(settings.log_level)
+    app.state.store = MonitorStore()
+    app.state.checker = EndpointChecker(settings)
+    app.state.ready = True
+    yield
+    app.state.ready = False
+
+
+app = FastAPI(title="Endpoint Monitor", version="0.1.0", lifespan=lifespan)
+
+
+def store() -> MonitorStore:
+    return app.state.store  # type: ignore[no-any-return]
+
+
+def checker() -> EndpointChecker:
+    return app.state.checker  # type: ignore[no-any-return]
+
+
+Store = Annotated[MonitorStore, Depends(store)]
+Checker = Annotated[EndpointChecker, Depends(checker)]
+
+
+def missing() -> HTTPException:
+    return HTTPException(status_code=404, detail="monitor not found")
+
+
+@app.get("/healthz")
+async def health() -> dict[str, str]:
+    return {"status": "ok"}
+
+
+@app.get("/readyz")
+async def readiness() -> dict[str, str]:
+    if not getattr(app.state, "ready", False):
+        raise HTTPException(status_code=503, detail="not ready")
+    return {"status": "ready"}
+
+
+@app.post("/v1/monitors", response_model=Monitor, status_code=status.HTTP_201_CREATED)
+async def create_monitor(payload: MonitorCreate, state: Store) -> Monitor:
+    return await state.create(payload)
+
+
+@app.get("/v1/monitors", response_model=list[Monitor])
+async def list_monitors(state: Store) -> list[Monitor]:
+    return await state.list()
+
+
+@app.get("/v1/monitors/{monitor_id}", response_model=Monitor)
+async def get_monitor(monitor_id: UUID, state: Store) -> Monitor:
+    item = await state.get(monitor_id)
+    if item is None:
+        raise missing()
+    return item
+
+
+@app.patch("/v1/monitors/{monitor_id}", response_model=Monitor)
+async def update_monitor(monitor_id: UUID, payload: MonitorUpdate, state: Store) -> Monitor:
+    if not payload.model_fields_set:
+        raise HTTPException(status_code=422, detail="at least one field is required")
+    item = await state.update(monitor_id, payload)
+    if item is None:
+        raise missing()
+    return item
+
+
+@app.delete("/v1/monitors/{monitor_id}", status_code=status.HTTP_204_NO_CONTENT)
+async def delete_monitor(monitor_id: UUID, state: Store) -> Response:
+    if not await state.delete(monitor_id):
+        raise missing()
+    return Response(status_code=status.HTTP_204_NO_CONTENT)
+
+
+@app.get("/v1/monitors/{monitor_id}/status", response_model=CurrentStatus)
+async def current_status(monitor_id: UUID, state: Store) -> CurrentStatus:
+    item = await state.get(monitor_id)
+    if item is None:
+        raise missing()
+    return item.current_status
+
+
+@app.post("/v1/monitors/{monitor_id}/check", response_model=CurrentStatus)
+async def check_monitor(monitor_id: UUID, state: Store, worker: Checker) -> CurrentStatus:
+    item = await state.get(monitor_id)
+    if item is None:
+        raise missing()
+    try:
+        result = await worker.check(str(monitor_id), str(item.url))
+    except DestinationRejected as exc:
+        result = CurrentStatus(
+            state=State.ERROR, checked_at=datetime.now(UTC), error=str(exc)[:200]
+        )
+        if await state.set_status(monitor_id, result) is None:
+            raise missing() from exc
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    if await state.set_status(monitor_id, result) is None:
+        raise missing()
+    return result