diff --git a/swh/core/config.py b/swh/core/config.py
--- a/swh/core/config.py
+++ b/swh/core/config.py
@@ -286,69 +286,23 @@
     return conf
 
 
-class SWHConfig:
-    """Mixin to add configuration parsing abilities to classes
+def load_from_envvar(default_config: Optional[Dict[str, Any]] = None) -> Dict[str, Any]:
+    """Load configuration yaml file from the environment variable SWH_CONFIG_FILENAME,
+    eventually enriched with default configuration key/value from the default_config
+    dict if provided.
 
-    The class should override the class attributes:
-        - DEFAULT_CONFIG (default configuration to be parsed)
-        - CONFIG_BASE_FILENAME (the filename of the configuration to be used)
+    Returns:
+        Configuration dict
 
-    This class defines one classmethod, parse_config_file, which
-    parses a configuration file using the default config as set in the
-    class attribute.
+    Raises:
+        AssertionError if SWH_CONFIG_FILENAME is undefined
 
     """
-
-    DEFAULT_CONFIG = {}  # type: Dict[str, Tuple[str, Any]]
-    CONFIG_BASE_FILENAME = ""  # type: Optional[str]
-
-    @classmethod
-    def parse_config_file(
-        cls,
-        base_filename=None,
-        config_filename=None,
-        additional_configs=None,
-        global_config=True,
-    ):
-        """Parse the configuration file associated to the current class.
-
-        By default, parse_config_file will load the configuration
-        cls.CONFIG_BASE_FILENAME from one of the Software Heritage
-        configuration directories, in order, unless it is overridden
-        by base_filename or config_filename (which shortcuts the file
-        lookup completely).
-
-        Args:
-            - base_filename (str): overrides the default
-              cls.CONFIG_BASE_FILENAME
-            - config_filename (str): sets the file to parse instead of
-              the defaults set from cls.CONFIG_BASE_FILENAME
-            - additional_configs: (list of default configuration dicts)
-              allows to override or extend the configuration set in
-              cls.DEFAULT_CONFIG.
-            - global_config (bool): Load the global configuration (default:
-              True)
-        """
-
-        if config_filename:
-            config_filenames = [config_filename]
-        elif "SWH_CONFIG_FILENAME" in os.environ:
-            config_filenames = [os.environ["SWH_CONFIG_FILENAME"]]
-        else:
-            if not base_filename:
-                base_filename = cls.CONFIG_BASE_FILENAME
-            config_filenames = swh_config_paths(base_filename)
-        if not additional_configs:
-            additional_configs = []
-
-        full_default_config = merge_default_configs(
-            cls.DEFAULT_CONFIG, *additional_configs
-        )
-
-        config = {}
-        if global_config:
-            config = load_global_config()
-
-        config.update(priority_read(config_filenames, full_default_config))
-
-        return config
+    assert (
+        "SWH_CONFIG_FILENAME" in os.environ
+    ), "SWH_CONFIG_FILENAME environment variable is undefined."
+
+    cfg_path = os.environ["SWH_CONFIG_FILENAME"]
+    cfg = read_raw_config(config_basepath(cfg_path))
+    cfg = merge_configs(default_config or {}, cfg)
+    return cfg
diff --git a/swh/core/tests/test_config.py b/swh/core/tests/test_config.py
--- a/swh/core/tests/test_config.py
+++ b/swh/core/tests/test_config.py
@@ -326,3 +326,39 @@
             config.merge_configs({"a": v}, {"a": {}})
         with pytest.raises(TypeError):
             config.merge_configs({"a": {}}, {"a": v})
+
+
+def test_load_from_envvar_no_environment_var_swh_config_filename_set():
+    """Without SWH_CONFIG_FILENAME set, load_from_envvar raises"""
+
+    with pytest.raises(AssertionError, match="SWH_CONFIG_FILENAME environment"):
+        config.load_from_envvar()
+
+
+def test_load_from_envvar_no_default_config(swh_config, monkeypatch):
+    config_path = str(swh_config)
+    monkeypatch.setenv("SWH_CONFIG_FILENAME", config_path)
+
+    actual_config = config.load_from_envvar()
+
+    expected_config = config.read(config_path)
+    assert actual_config == expected_config
+
+
+def test_load_from_envvar_with_default_config(swh_config, monkeypatch):
+    default_config = {
+        "number": 666,
+        "something-cool": ["something", "cool"],
+    }
+
+    config_path = str(swh_config)
+    monkeypatch.setenv("SWH_CONFIG_FILENAME", config_path)
+
+    actual_config = config.load_from_envvar(default_config)
+
+    expected_config = config.read(config_path)
+    expected_config.update(
+        {"number": 666, "something-cool": ["something", "cool"],}
+    )
+
+    assert actual_config == expected_config