diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index b421be2a..73ef26dc 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -29,7 +29,7 @@ repos:
         args: [ --config-file, pyproject.toml ]
         pass_filenames: false
         additional_dependencies:
-          - neptune-api==0.7.0b
+          - neptune-api
           - more-itertools
           - backoff
 default_language_version:
diff --git a/src/neptune_scale/net/api_client.py b/src/neptune_scale/net/api_client.py
index a6cf90c2..1bbcccfd 100644
--- a/src/neptune_scale/net/api_client.py
+++ b/src/neptune_scale/net/api_client.py
@@ -27,9 +27,11 @@
 from typing import (
     Any,
     Literal,
+    cast,
 )
 
 import httpx
+import neptune_retrieval_api.client
 from httpx import Timeout
 from neptune_api import (
     AuthenticatedClient,
@@ -64,6 +66,11 @@
 from neptune_api.proto.neptune_pb.ingest.v1.pub.ingest_pb2 import RunOperation
 from neptune_api.proto.neptune_pb.ingest.v1.pub.request_status_pb2 import RequestStatus
 from neptune_api.types import Response
+from neptune_retrieval_api.api.default import search_leaderboard_entries_proto
+from neptune_retrieval_api.models import SearchLeaderboardEntriesParamsDTO
+from neptune_retrieval_api.proto.neptune_pb.api.v1.model.leaderboard_entries_pb2 import (
+    ProtoLeaderboardEntriesSearchResultDTO,
+)
 
 from neptune_scale.exceptions import (
     NeptuneConnectionLostError,
@@ -129,6 +136,11 @@ def submit(self, operation: RunOperation, family: str) -> Response[SubmitRespons
     @abc.abstractmethod
     def check_batch(self, request_ids: list[str], project: str) -> Response[BulkRequestStatus]: ...
 
+    @abc.abstractmethod
+    def search_entries(
+        self, project_id: str, body: SearchLeaderboardEntriesParamsDTO
+    ) -> ProtoLeaderboardEntriesSearchResultDTO: ...
+
 
 class HostedApiClient(ApiClient):
     def __init__(self, api_token: str) -> None:
@@ -141,6 +153,9 @@ def __init__(self, api_token: str) -> None:
         self.backend = create_auth_api_client(
             credentials=credentials, config=config, token_refreshing_urls=token_urls, verify_ssl=verify_ssl
         )
+        # This is required only to silence mypy. The two client objects are compatible, because they're
+        # generated by swagger codegen.
+        self.retrieval_backend = cast(neptune_retrieval_api.client.AuthenticatedClient, self.backend)
         logger.debug("Connected to Neptune API")
 
     def submit(self, operation: RunOperation, family: str) -> Response[SubmitResponse]:
@@ -153,6 +168,15 @@ def check_batch(self, request_ids: list[str], project: str) -> Response[BulkRequ
             body=RequestIdList(ids=[RequestId(value=request_id) for request_id in request_ids]),
         )
 
+    def search_entries(
+        self, project_id: str, body: SearchLeaderboardEntriesParamsDTO
+    ) -> ProtoLeaderboardEntriesSearchResultDTO:
+        resp = search_leaderboard_entries_proto.sync_detailed(
+            client=self.retrieval_backend, project_identifier=project_id, type=["run"], body=body
+        )
+        result = ProtoLeaderboardEntriesSearchResultDTO.FromString(resp.content)
+        return result
+
     def close(self) -> None:
         logger.debug("Closing API client")
         self.backend.__exit__()
@@ -181,6 +205,11 @@ def check_batch(self, request_ids: list[str], project: str) -> Response[BulkRequ
         )
         return Response(content=b"", parsed=response_body, status_code=HTTPStatus.OK, headers={})
 
+    def search_entries(
+        self, project_id: str, body: SearchLeaderboardEntriesParamsDTO
+    ) -> ProtoLeaderboardEntriesSearchResultDTO:
+        return ProtoLeaderboardEntriesSearchResultDTO()
+
 
 def backend_factory(api_token: str, mode: Literal["async", "disabled"]) -> ApiClient:
     if mode == "disabled":
diff --git a/src/neptune_scale/net/projects.py b/src/neptune_scale/net/projects.py
index ce698ada..4a97de2d 100644
--- a/src/neptune_scale/net/projects.py
+++ b/src/neptune_scale/net/projects.py
@@ -1,4 +1,3 @@
-import os
 import re
 from enum import Enum
 from json import JSONDecodeError
@@ -11,7 +10,6 @@
 import httpx
 
 from neptune_scale.exceptions import (
-    NeptuneApiTokenNotProvided,
     NeptuneBadRequestError,
     NeptuneProjectAlreadyExists,
 )
@@ -19,7 +17,7 @@
     HostedApiClient,
     with_api_errors_handling,
 )
-from neptune_scale.util.envs import API_TOKEN_ENV_NAME
+from neptune_scale.sync.util import ensure_api_token
 
 PROJECTS_PATH_BASE = "/api/backend/v1/projects"
 
@@ -33,14 +31,6 @@ class ProjectVisibility(Enum):
 ORGANIZATION_NOT_FOUND_RE = re.compile(r"Organization .* not found")
 
 
-def _get_api_token(api_token: Optional[str]) -> str:
-    api_token = api_token or os.environ.get(API_TOKEN_ENV_NAME)
-    if api_token is None:
-        raise NeptuneApiTokenNotProvided()
-
-    return api_token
-
-
 @with_api_errors_handling
 def create_project(
     workspace: str,
@@ -52,9 +42,7 @@ def create_project(
     fail_if_exists: bool = False,
     api_token: Optional[str] = None,
 ) -> None:
-    api_token = _get_api_token(api_token)
-
-    client = HostedApiClient(api_token=api_token)
+    client = HostedApiClient(api_token=ensure_api_token(api_token))
     visibility = ProjectVisibility(visibility)
 
     body = {
@@ -92,7 +80,7 @@ def _safe_json(response: httpx.Response) -> Any:
 
 
 def get_project_list(*, api_token: Optional[str] = None) -> list[dict]:
-    client = HostedApiClient(api_token=_get_api_token(api_token))
+    client = HostedApiClient(api_token=ensure_api_token(api_token))
 
     params = {
         "userRelation": "viewerOrHigher",
diff --git a/src/neptune_scale/net/runs.py b/src/neptune_scale/net/runs.py
new file mode 100644
index 00000000..bf14fe86
--- /dev/null
+++ b/src/neptune_scale/net/runs.py
@@ -0,0 +1,29 @@
+from typing import Optional
+
+from neptune_retrieval_api.models import SearchLeaderboardEntriesParamsDTO
+
+from neptune_scale.exceptions import NeptuneScaleError
+from neptune_scale.net.api_client import HostedApiClient
+from neptune_scale.net.util import escape_nql_criterion
+from neptune_scale.sync.util import ensure_api_token
+
+
+def run_exists(project: str, run_id: str, api_token: Optional[str] = None) -> bool:
+    """Query the backend for the existence of a Run with the given ID.
+
+    Returns True if the Run exists, False otherwise.
+    """
+
+    client = HostedApiClient(api_token=ensure_api_token(api_token))
+    body = SearchLeaderboardEntriesParamsDTO.from_dict(
+        {
+            "query": {"query": f'`sys/custom_run_id`:string = "{escape_nql_criterion(run_id)}"'},
+        }
+    )
+
+    try:
+        result = client.search_entries(project, body)
+    except Exception as e:
+        raise NeptuneScaleError(reason=e)
+
+    return bool(result.entries)
diff --git a/src/neptune_scale/net/util.py b/src/neptune_scale/net/util.py
new file mode 100644
index 00000000..cbc25d2e
--- /dev/null
+++ b/src/neptune_scale/net/util.py
@@ -0,0 +1,6 @@
+def escape_nql_criterion(criterion: str) -> str:
+    """
+    Escape backslash and (double-)quotes in the string, to match what the NQL engine expects.
+    """
+
+    return criterion.replace("\\", r"\\").replace('"', r"\"")
diff --git a/src/neptune_scale/sync/util.py b/src/neptune_scale/sync/util.py
index 60fe4b0b..2d5ecf96 100644
--- a/src/neptune_scale/sync/util.py
+++ b/src/neptune_scale/sync/util.py
@@ -1,4 +1,9 @@
+import os
 import signal
+from typing import Optional
+
+from neptune_scale.exceptions import NeptuneApiTokenNotProvided
+from neptune_scale.util.envs import API_TOKEN_ENV_NAME
 
 
 def safe_signal_name(signum: int) -> str:
@@ -8,3 +13,13 @@ def safe_signal_name(signum: int) -> str:
         signame = str(signum)
 
     return signame
+
+
+def ensure_api_token(api_token: Optional[str]) -> str:
+    """Ensure the API token is provided via either explicit argument, or env variable."""
+
+    api_token = api_token or os.environ.get(API_TOKEN_ENV_NAME)
+    if api_token is None:
+        raise NeptuneApiTokenNotProvided()
+
+    return api_token
diff --git a/tests/e2e/test_net.py b/tests/e2e/test_net.py
new file mode 100644
index 00000000..263def20
--- /dev/null
+++ b/tests/e2e/test_net.py
@@ -0,0 +1,10 @@
+import os
+
+from neptune_scale.net.runs import run_exists
+
+NEPTUNE_PROJECT = os.getenv("NEPTUNE_E2E_PROJECT")
+
+
+def test_run_exists_true(run):
+    assert run_exists(run._project, run._run_id)
+    assert not run_exists(run._project, "nonexistent_run_id")
diff --git a/tests/unit/test_process_link.py b/tests/unit/test_process_link.py
index f3f68ec3..c030a268 100644
--- a/tests/unit/test_process_link.py
+++ b/tests/unit/test_process_link.py
@@ -169,7 +169,7 @@ def on_closed(_):
 
     link.start(on_link_closed=on_closed)
     # We should never finish the sleep call, as on_closed raises SystemExit
-    time.sleep(5)
+    time.sleep(10)
     assert False, "on_closed callback was not called"
 
 
@@ -184,5 +184,5 @@ def test_parent_termination():
     p = multiprocessing.Process(target=parent, args=(var, event))
     p.start()
 
-    assert event.wait(1)
+    assert event.wait(5)
     assert var.value == 1