diff --git a/src/openeo_aggregator/backend.py b/src/openeo_aggregator/backend.py
index 138bbbb6..788743d6 100644
--- a/src/openeo_aggregator/backend.py
+++ b/src/openeo_aggregator/backend.py
@@ -30,8 +30,17 @@
 from openeo_aggregator.metadata.reporter import LoggerReporter
 from openeo_aggregator.partitionedjobs import PartitionedJob
 from openeo_aggregator.partitionedjobs.splitting import FlimsySplitter, TileGridSplitter
-from openeo_aggregator.partitionedjobs.tracking import PartitionedJobConnection, PartitionedJobTracker
-from openeo_aggregator.utils import subdict, dict_merge, normalize_issuer_url
+from openeo_aggregator.partitionedjobs.tracking import (
+    PartitionedJobConnection,
+    PartitionedJobTracker,
+)
+from openeo_aggregator.utils import (
+    subdict,
+    dict_merge,
+    normalize_issuer_url,
+    FlatPG,
+    PGWithMetadata,
+)
 from openeo_driver.ProcessGraphDeserializer import SimpleProcessing
 from openeo_driver.backend import OpenEoBackendImplementation, AbstractCollectionCatalog, LoadParameters, Processing, \
     OidcProvider, BatchJobs, BatchJobMetadata, SecondaryServices, ServiceMetadata
@@ -395,7 +404,7 @@ def evaluate(self, process_graph: dict, env: EvalEnv = None):
 
         return streaming_flask_response(backend_response, chunk_size=self._stream_chunk_size)
 
-    def preprocess_process_graph(self, process_graph: dict, backend_id: str) -> dict:
+    def preprocess_process_graph(self, process_graph: FlatPG, backend_id: str) -> dict:
         def preprocess(node: Any) -> Any:
             if isinstance(node, dict):
                 if "process_id" in node and "arguments" in node:
@@ -538,7 +547,12 @@ def _create_job_standard(
         )
 
     def _create_partitioned_job(
-            self, user_id: str, process: dict, api_version: str, metadata: dict, job_options: dict = None
+        self,
+        user_id: str,
+        process: PGWithMetadata,
+        api_version: str,
+        metadata: dict,
+        job_options: dict = None,
     ) -> BatchJobMetadata:
         """
         Advanced/handled batch job creation:
diff --git a/src/openeo_aggregator/partitionedjobs/__init__.py b/src/openeo_aggregator/partitionedjobs/__init__.py
index 3d347c0c..607d196e 100644
--- a/src/openeo_aggregator/partitionedjobs/__init__.py
+++ b/src/openeo_aggregator/partitionedjobs/__init__.py
@@ -1,5 +1,6 @@
-from typing import NamedTuple, List
+from typing import NamedTuple, List, Dict
 
+from openeo_aggregator.utils import FlatPG, PGWithMetadata
 from openeo_driver.errors import OpenEOApiException
 
 
@@ -10,7 +11,7 @@ class PartitionedJobFailure(OpenEOApiException):
 class SubJob(NamedTuple):
     """A part of a partitioned job, target at a particular, single back-end."""
     # Process graph of the subjob (derived in some way from original parent process graph)
-    process_graph: dict
+    process_graph: FlatPG
     # Id of target backend
     backend_id: str
 
@@ -18,7 +19,7 @@ class SubJob(NamedTuple):
 class PartitionedJob(NamedTuple):
     """A large or multi-back-end job that is split in several sub jobs"""
     # Original process graph
-    process: dict
+    process: PGWithMetadata
     metadata: dict
     job_options: dict
     # List of sub-jobs
diff --git a/src/openeo_aggregator/partitionedjobs/splitting.py b/src/openeo_aggregator/partitionedjobs/splitting.py
index 9cd28240..bbfe0679 100644
--- a/src/openeo_aggregator/partitionedjobs/splitting.py
+++ b/src/openeo_aggregator/partitionedjobs/splitting.py
@@ -10,7 +10,7 @@
 
 from openeo.internal.process_graph_visitor import ProcessGraphVisitor
 from openeo_aggregator.partitionedjobs import PartitionedJob, SubJob, PartitionedJobFailure
-from openeo_aggregator.utils import BoundingBox
+from openeo_aggregator.utils import BoundingBox, PGWithMetadata, FlatPG
 from openeo_driver.ProcessGraphDeserializer import convert_node, ENV_DRY_RUN_TRACER, ConcreteProcessing
 from openeo_driver.backend import OpenEoBackendImplementation
 from openeo_driver.dry_run import DryRunDataTracer
@@ -38,7 +38,9 @@ class AbstractJobSplitter(metaclass=abc.ABCMeta):
     """
 
     @abc.abstractmethod
-    def split(self, process: dict, metadata: dict = None, job_options: dict = None) -> PartitionedJob:
+    def split(
+        self, process: PGWithMetadata, metadata: dict = None, job_options: dict = None
+    ) -> PartitionedJob:
         # TODO: how to express dependencies? give SubJobs an id for referencing?
         # TODO: how to express combination/aggregation of multiple subjob results as a final result?
         ...
@@ -54,7 +56,9 @@ class FlimsySplitter(AbstractJobSplitter):
     def __init__(self, processing: "AggregatorProcessing"):
         self.processing = processing
 
-    def split(self, process: dict, metadata: dict = None, job_options: dict = None) -> PartitionedJob:
+    def split(
+        self, process: PGWithMetadata, metadata: dict = None, job_options: dict = None
+    ) -> PartitionedJob:
         process_graph = process["process_graph"]
         backend_id = self.processing.get_backend_for_process_graph(process_graph=process_graph, api_version="TODO")
         process_graph = self.processing.preprocess_process_graph(process_graph, backend_id=backend_id)
@@ -142,7 +146,9 @@ def __init__(self, processing: "AggregatorProcessing"):
             processing=processing
         )
 
-    def split(self, process: dict, metadata: dict = None, job_options: dict = None) -> PartitionedJob:
+    def split(
+        self, process: PGWithMetadata, metadata: dict = None, job_options: dict = None
+    ) -> PartitionedJob:
         # TODO: refactor process graph preprocessing and backend_id getting in reusable AbstractJobSplitter method?
         processing: AggregatorProcessing = self.backend_implementation.processing
         process_graph = process["process_graph"]
@@ -171,7 +177,7 @@ def split(self, process: dict, metadata: dict = None, job_options: dict = None)
 
         return PartitionedJob(process=process, metadata=metadata, job_options=job_options, subjobs=subjobs)
 
-    def _extract_global_spatial_extent(self, process: dict) -> BoundingBox:
+    def _extract_global_spatial_extent(self, process: PGWithMetadata) -> BoundingBox:
         """Extract global spatial extent from given process graph"""
         # TODO: drop deepcopy when `dereference_from_node_arguments` doesn't do
         #       in-place manipulation of original process dict anymore
@@ -198,7 +204,9 @@ def _extract_global_spatial_extent(self, process: dict) -> BoundingBox:
         global_extent = BoundingBox.from_dict(spatial_extent_union(*spatial_extents))
         return global_extent
 
-    def _filter_bbox_injector(self, process_graph: dict) -> typing.Callable[[BoundingBox], dict]:
+    def _filter_bbox_injector(
+        self, process_graph: FlatPG
+    ) -> typing.Callable[[BoundingBox], dict]:
         """
         Build function that takes a bounding box and injects a filter_bbox node
         just before result the `save_result` node of a "template" process graph.
diff --git a/src/openeo_aggregator/utils.py b/src/openeo_aggregator/utils.py
index 1ba3b2b7..5bf9046c 100644
--- a/src/openeo_aggregator/utils.py
+++ b/src/openeo_aggregator/utils.py
@@ -17,6 +17,17 @@
 _log = logging.getLogger(__name__)
 
 
+# Type-hinting alias for "process graph with metadata" constructs:
+# containing at least a "process_graph" field with a process graph in "flat-graph" representation
+# TODO move this upstream to openeo-python-driver
+PGWithMetadata = dict
+
+
+# Type-hinting alias for process graphs in "flat-graph" representation.
+# TODO move this upstream to openeo-python-driver
+FlatPG = dict
+
+
 class MultiDictGetter:
     """
     Helper to get (and combine) items (where available) from a collection of dictionaries.