diff --git a/.github/workflows/ci_job.yml b/.github/workflows/ci_job.yml
index 4eebc7a3..2959c1cc 100644
--- a/.github/workflows/ci_job.yml
+++ b/.github/workflows/ci_job.yml
@@ -87,6 +87,7 @@ jobs:
             pip
             cfgrib
             xarray
+            xarray-prism
             cffi
             py-oidc-auth-fastapi
           condarc: |
diff --git a/Dockerfile b/Dockerfile
index 2fa5b072..ffab348b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -53,6 +53,7 @@ session required pam_sss.so\n\
         redis-py \
         requests \
         watchfiles \
+        xarray-prism \
         zarr; \
     elif [ "${CMD}" = "freva-rest-server" ];then\
         PKGNAME=freva-rest && \
@@ -82,6 +83,7 @@ session required pam_sss.so\n\
         uvicorn \
         tomli \
         xarray \
+        xarray-prism \
         py-oidc-auth-fastapi \
         zarr; \
     else \
diff --git a/freva-client/pyproject.toml b/freva-client/pyproject.toml
index 8f1624bb..438959e0 100644
--- a/freva-client/pyproject.toml
+++ b/freva-client/pyproject.toml
@@ -45,7 +45,7 @@ Source = "https://github.com/freva-org/freva-nextgen/"
 
 [project.optional-dependencies]
 dev = ["tox"]
-tests = ["namegenerator"]
+tests = []
 
 [tool.flit.sdist]
 include = ["assets/*"]
diff --git a/freva-data-portal-worker/data-loader b/freva-data-portal-worker/data-loader
index 6fc35150..dc5c05cd 100644
--- a/freva-data-portal-worker/data-loader
+++ b/freva-data-portal-worker/data-loader
@@ -26,7 +26,8 @@ jq \
 mamba \
 netcdf4 \
 rasterio \
-zarr"
+zarr \
+xarray-prism"
 
 
 # Generate a checksum of the package list
diff --git a/freva-data-portal-worker/pyproject.toml b/freva-data-portal-worker/pyproject.toml
index 05f2fee6..9178f679 100644
--- a/freva-data-portal-worker/pyproject.toml
+++ b/freva-data-portal-worker/pyproject.toml
@@ -28,6 +28,7 @@ dependencies = [
 "bokeh",
 "cloudpickle",
 "dask[distributed,diagnostics]",
+"xarray-prism",
 "h5netcdf",
 "jupyter-server-proxy",
 "packaging",
diff --git a/freva-data-portal-worker/src/data_portal_worker/_cache_manager.py b/freva-data-portal-worker/src/data_portal_worker/_cache_manager.py
new file mode 100644
index 00000000..b1788781
--- /dev/null
+++ b/freva-data-portal-worker/src/data_portal_worker/_cache_manager.py
@@ -0,0 +1,47 @@
+"""Periodic cache cleanup for xarray-prism downloaded files."""
+
+from __future__ import annotations
+
+import os
+import time
+
+from .utils import data_logger
+
+# How often to run eviction (seconds). Default: every 6 hours.
+_CLEANUP_INTERVAL = float(os.environ.get("API_CACHE_CLEANUP_INTERVAL", 6 * 3600))
+
+
+def run_cache_cleanup(force: bool = False) -> None:
+    """Evict stale/oversized xarray-prism cache files safely.
+    """
+    try:
+        import xarray_prism
+
+        xarray_prism.clear_cache()
+        info = xarray_prism.cache_info()
+        data_logger.info(
+            "Cache cleanup done: %d file(s), %.1f MB remaining at %s",
+            info["files"],
+            info["size_bytes"] / 1024**2,
+            info["path"],
+        )
+    except Exception as error:
+        # housekeeping never break the data-loading daemon
+        # on 6-hourly cleanup attempts, only warns on failure
+        data_logger.warning("Cache cleanup failed (non-fatal): %s", error)
+
+
+class CacheScheduler:
+    """Tracks elapsed time and fires cleanup when interval is due."""
+
+    def __init__(self) -> None:
+        # run immediately on first tick,
+        # then every _CLEANUP_INTERVAL
+        # seconds thereafter
+        self._last_run: float = 0.0
+
+    def tick(self) -> None:
+        """Call on every iteration of the daemon loop."""
+        if time.monotonic() - self._last_run >= _CLEANUP_INTERVAL:
+            self._last_run = time.monotonic()
+            run_cache_cleanup()
diff --git a/freva-data-portal-worker/src/data_portal_worker/backends/posix_and_cloud.py b/freva-data-portal-worker/src/data_portal_worker/backends/posix_and_cloud.py
index 9ab7233e..29bbd958 100644
--- a/freva-data-portal-worker/src/data_portal_worker/backends/posix_and_cloud.py
+++ b/freva-data-portal-worker/src/data_portal_worker/backends/posix_and_cloud.py
@@ -1,70 +1,24 @@
 """Load data."""
 
 from pathlib import Path
-from typing import Any, Optional, Union
+from typing import Any, Union
 from urllib.parse import urlparse
 
-import h5netcdf
-import netCDF4
-import rasterio
 import xarray as xr
-import zarr
-
-from data_portal_worker.utils import data_logger
-
-try:
-    import cfgrib
-except (ImportError, RuntimeError):  # pragma: no cover
-    data_logger.warning("Could not import cfgrib, loading GRB files is disabled")
-
-
-def get_xr_engine(file_path: str) -> Optional[str]:
-    """Get the engine, to open the xarray dataset."""
-    try:
-        with netCDF4.Dataset(file_path, mode="r"):
-            return "netcdf4"
-    except Exception:
-        pass
-
-    try:
-        with cfgrib.open_file(file_path):
-            return "cfgrib"  # pragma: no cover
-    except Exception:
-        pass
-    try:
-        _ = zarr.open(file_path, mode="r")
-        return "zarr"
-    except Exception:
-        pass
-
-    try:
-        with rasterio.open(file_path, mode="r"):
-            return "rasterio"
-    except Exception:
-        pass
-
-    try:
-        with h5netcdf.File(file_path, mode="r"):
-            return "h5netcdf"
-    except Exception:
-        pass
-
-    return None
 
 
 def posix_and_cloud(
     inp_file: Union[str, Path], chunk_size: float = 16.0, **kwargs: Any
 ) -> xr.Dataset:
     """Open a dataset with xarray."""
+    engine = "prism"
     inp_str = str(inp_file)
     parsed = urlparse(inp_str)
     target: Union[str, Path]
     target = Path(inp_str) if parsed.scheme in ("", "file") else inp_str
-    engine = get_xr_engine(str(target))
     _ = kwargs.pop("chunks", None)
-    for key in ("decode_cf", "use_cftime", "cache", "decode_coords"):
+    for key in ("decode_cf", "cache", "decode_coords"):
         kwargs[key] = False
+    kwargs["chunks"] = "auto"
     kwargs["engine"] = engine
-    if engine != "h5netcdf":
-        kwargs["chunks"] = "auto"
     return xr.open_dataset(target, **kwargs).unify_chunks()
diff --git a/freva-data-portal-worker/src/data_portal_worker/load_data.py b/freva-data-portal-worker/src/data_portal_worker/load_data.py
index 02970e17..942990ee 100644
--- a/freva-data-portal-worker/src/data_portal_worker/load_data.py
+++ b/freva-data-portal-worker/src/data_portal_worker/load_data.py
@@ -29,6 +29,7 @@
 from redis.retry import Retry
 from xarray.backends.zarr import encode_zarr_variable
 
+from ._cache_manager import CacheScheduler
 from .aggregator import DatasetAggregator, write_grouped_zarr
 from .backends import load_data
 from .rechunker import ChunkOptimizer
@@ -391,12 +392,14 @@ def run_for_ever(self, channel: str) -> None:
         """Start the listener daemon."""
         data_logger.info("Starting data-loading daemon")
         pubsub: Optional[PubSub] = None
+        cache_scheduler = CacheScheduler()
         data_logger.info("Broker will listen for messages now")
         while True:
             try:
                 if pubsub is None:
                     pubsub = self.cache.pubsub()
                     pubsub.subscribe(channel)
+                cache_scheduler.tick()
                 message = pubsub.get_message()
                 if message and message["type"] == "message":
                     self.redis_callback(message["data"])
diff --git a/tests/client/test_databrowser_cli.py b/tests/client/test_databrowser_cli.py
index 4fcd4b06..8fbc1336 100644
--- a/tests/client/test_databrowser_cli.py
+++ b/tests/client/test_databrowser_cli.py
@@ -15,7 +15,6 @@
 from pathlib import Path
 from tempfile import NamedTemporaryFile
 
-import namegenerator
 from py_oidc_auth_client import Token
 from pytest import LogCaptureFixture
 from pytest_mock import MockerFixture
@@ -664,8 +663,8 @@ def test_flavour_full_lifecycle(
         mocker.patch("freva_client.utils.choose_token_strategy").return_value = (
             "use_token"
         )
-
-        flavour_name = namegenerator.gen()
+        from freva_rest.utils.namegenerator import generate_names
+        flavour_name = generate_names()
         res = cli_runner.invoke(
             app,
             [
diff --git a/tests/client/test_databrowser_py.py b/tests/client/test_databrowser_py.py
index 580ab81b..e0580f90 100644
--- a/tests/client/test_databrowser_py.py
+++ b/tests/client/test_databrowser_py.py
@@ -12,7 +12,6 @@
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
-import namegenerator
 import pandas as pd
 import pytest
 from py_oidc_auth_client import Token
@@ -520,7 +519,8 @@ def test_flavour_lifecycle(
     ) -> None:
         """Test the full lifecycle: list, add, update, rename, delete."""
         # list existing flavours
-        flavour_name = namegenerator.gen()
+        from freva_rest.utils.namegenerator import generate_names
+        flavour_name = generate_names()
         mocker.patch("freva_client.utils.choose_token_strategy").return_value = (
             "use_token"
         )
diff --git a/tests/data_portal/test_cache_manager.py b/tests/data_portal/test_cache_manager.py
new file mode 100644
index 00000000..c3a45e2d
--- /dev/null
+++ b/tests/data_portal/test_cache_manager.py
@@ -0,0 +1,84 @@
+"""tests for _cache_manager."""
+ 
+from __future__ import annotations
+ 
+from unittest.mock import MagicMock, patch
+ 
+import pytest
+import data_portal_worker._cache_manager as cm
+ 
+ 
+def test_run_cache_cleanup_happy_path() -> None:
+    """Successful cleanup logs info and does not raise."""
+    mock_prism = MagicMock()
+    mock_prism.cache_info.return_value = {
+        "files": 3,
+        "size_bytes": 1024 ** 2 * 8,
+        "path": "/tmp/prism_cache",
+    }
+    with patch.dict("sys.modules", {"xarray_prism": mock_prism}):
+        cm.run_cache_cleanup()
+ 
+    mock_prism.clear_cache.assert_called_once()
+    mock_prism.cache_info.assert_called_once()
+ 
+ 
+def test_run_cache_cleanup_logs_warning_on_error() -> None:
+    """Any exception inside cleanup is caught and logged as a warning."""
+    mock_prism = MagicMock()
+    mock_prism.clear_cache.side_effect = RuntimeError("disk full")
+
+    with patch.dict("sys.modules", {"xarray_prism": mock_prism}):
+        with patch.object(cm.data_logger, "warning") as mock_warn:
+            cm.run_cache_cleanup()
+
+    mock_warn.assert_called_once()
+    assert "Cache cleanup failed" in mock_warn.call_args[0][0]
+ 
+
+ 
+def test_scheduler_fires_immediately_on_first_tick(monkeypatch: pytest.MonkeyPatch) -> None:
+    """tick() should call run_cache_cleanup on the very first call."""
+    calls: list[int] = []
+    monkeypatch.setattr(cm, "run_cache_cleanup", lambda: calls.append(1))
+    scheduler = cm.CacheScheduler()
+    scheduler._last_run = float("-inf")
+    scheduler.tick()
+    assert calls == [1]
+
+
+def test_scheduler_does_not_fire_twice_within_interval(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A second tick() shortly after the first should not fire again."""
+    calls: list[int] = []
+    monkeypatch.setattr(cm, "run_cache_cleanup", lambda: calls.append(1))
+    scheduler = cm.CacheScheduler()
+    scheduler._last_run = float("-inf")
+    scheduler.tick()
+    # too soon
+    scheduler.tick()
+    assert len(calls) == 1
+
+
+def test_scheduler_fires_again_after_interval(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """tick() fires again once the interval has elapsed."""
+    calls: list[int] = []
+    monkeypatch.setattr(cm, "run_cache_cleanup", lambda: calls.append(1))
+
+    scheduler = cm.CacheScheduler()
+    scheduler._last_run = float("-inf")
+    scheduler.tick()          
+    scheduler._last_run = float("-inf")
+    scheduler.tick()          
+    assert len(calls) == 2
+
+
+def test_cleanup_interval_env_var(monkeypatch: pytest.MonkeyPatch) -> None:
+    """_CLEANUP_INTERVAL should reflect API_CACHE_CLEANUP_INTERVAL."""
+    monkeypatch.setenv("API_CACHE_CLEANUP_INTERVAL", "42")
+    import importlib
+    importlib.reload(cm)
+    assert cm._CLEANUP_INTERVAL == 42.0
diff --git a/tests/data_portal/test_load_utils.py b/tests/data_portal/test_load_utils.py
index 6d858358..42d3d1fe 100644
--- a/tests/data_portal/test_load_utils.py
+++ b/tests/data_portal/test_load_utils.py
@@ -8,7 +8,6 @@
 import rasterio
 import zarr
 from unittest.mock import patch
-from data_portal_worker.backends.posix_and_cloud import get_xr_engine
 from data_portal_worker.utils import str_to_int as str_to_int2
 from freva_rest.utils.base_utils import get_userinfo, str_to_int
 
@@ -64,14 +63,3 @@ def test_get_auth_userinfo() -> None:
     assert out["last_name"] == "Doe"
     assert out["first_name"] == "Jane"
 
-
-def test_get_xr_posix_engine() -> None:
-    """Test the right xarray engine."""
-    with TemporaryDirectory() as temp_dir:
-        assert get_xr_engine(create_netcdf4_file(temp_dir)) == "netcdf4"
-        assert get_xr_engine(create_rasterio_file(temp_dir)) == "rasterio"
-        assert get_xr_engine(create_zarr_file(temp_dir)) == "zarr"
-        with patch("h5netcdf.File"):
-            assert get_xr_engine("http://example.com/data.nc") == "h5netcdf"
-    with TemporaryDirectory() as temp_dir:
-        assert get_xr_engine(temp_dir) is None