diff --git a/agent/database_optimizer.py b/agent/database_optimizer.py
index 7a56bff6..8e8695e4 100644
--- a/agent/database_optimizer.py
+++ b/agent/database_optimizer.py
@@ -242,8 +242,7 @@ def potential_indexes(self) -> list[DBIndex]:
         # Top N query variant - Order by column can possibly speed up the query
         if (
             order_by_columns := self.parsed_query.columns_dict.get("order_by")
-            and self.parsed_query.limit_and_offset
-        ):
+        ) and self.parsed_query.limit_and_offset:
             possible_indexes.extend(order_by_columns)
 
         possible_db_indexes = [self._convert_to_db_index(i) for i in possible_indexes]
diff --git a/agent/tests/test_database_optimizer.py b/agent/tests/test_database_optimizer.py
new file mode 100644
index 00000000..a05ae92c
--- /dev/null
+++ b/agent/tests/test_database_optimizer.py
@@ -0,0 +1,659 @@
+from __future__ import annotations
+
+import json
+import unittest
+
+from agent.database_optimizer import DBExplain, DBOptimizer, DBTable
+
+
+class TestDatabaseOptimizer(unittest.TestCase):
+    def test_basic_index_existence_analysis(self):
+        def possible_indexes(q):
+            user = DBTable.from_frappe_output(USER_TABLE)
+            has_role = DBTable.from_frappe_output(HAS_ROLE_TABLE)
+            return [
+                i.column
+                for i in DBOptimizer(
+                    query=q,
+                    tables={"tabUser": user, "tabHas Role": has_role},
+                ).potential_indexes()
+            ]
+
+        self.assertEqual(
+            ["creation"],
+            possible_indexes("select `name` from `tabUser` order by `creation` desc limit 1"),
+        )
+
+        self.assertEqual(
+            ["full_name"],
+            possible_indexes("select `name` from `tabUser` where full_name = 'xyz'"),
+        )
+
+        self.assertIn(
+            "user",
+            possible_indexes("select `name` from `tabUser` u join `tabHas Role` h on h.user = u.name"),
+        )
+
+    def test_suggestion_using_table_stats(self):
+        user = DBTable.from_frappe_output(USER_TABLE)
+        has_role = DBTable.from_frappe_output(HAS_ROLE_TABLE)
+
+        tables = {"tabUser": user, "tabHas Role": has_role}
+        self.assertEqual(user.total_rows, 92)
+
+        # This should suggest adding api_key as it definitely has highest cardinality.
+        optimizer = DBOptimizer(
+            query="select name from tabUser where enabled = 1 and api_key = 'xyz'", tables=tables
+        )
+        self.assertIn("api_key", [i.column for i in optimizer.potential_indexes()])
+
+        index = optimizer.suggest_index()
+        self.assertEqual(index.column, "api_key")
+
+        # This should suggest nothing as modified is already indexed
+        optimizer = DBOptimizer(
+            query="select name from tabUser order by modified asc",
+            tables=tables,
+        )
+        self.assertIsNone(optimizer.suggest_index())
+
+        # This should suggest nothing as modified is already indexed
+        optimizer = DBOptimizer(
+            query="select name from tabUser u join `tabHas Role` r on r.parent = u.name where r.role='System Manager'",  # noqa: E501
+            tables=tables,
+        )
+        index = optimizer.suggest_index()
+        self.assertEqual(index.column, "role")
+        self.assertEqual(index.table, "tabHas Role")
+
+    def test_complex_sub_query_aliases(self):
+        """Check if table identification is correct for subqueries."""
+
+        q = """SELECT *,
+                    (SELECT COUNT(*) FROM `tabHD Ticket Comment` WHERE `tabHD Ticket Comment`.`reference_ticket`=`tabHD Ticket`.`name`) `count_comment`,
+                    (SELECT COUNT(*) FROM `tabCommunication` WHERE `tabCommunication`.`reference_doctype`='HD Ticket' AND `tabCommunication`.`reference_name`=`tabHD Ticket`.`name`) `count_msg`,
+                FROM `tabHD Ticket`
+                WHERE `agent_group`='L2'
+                ORDER BY `modified` DESC
+                LIMIT 20
+            """  # noqa: E501
+        explain = [DBExplain.from_frappe_output(e) for e in json.loads(EXPLAIN_OUTPUT)]
+        optimizer = DBOptimizer(query=q, explain_plan=explain)
+        optimizer.update_table_data(DBTable.from_frappe_output(HD_TICKET_TABLE))
+        optimizer.update_table_data(DBTable.from_frappe_output(HD_TICKET_COMMENT_TABLE))
+        optimizer.update_table_data(DBTable.from_frappe_output(COMMUNICATION_TABLE))
+
+        self.assertTrue(optimizer.can_be_optimized())
+        index = optimizer.suggest_index()
+        self.assertEqual(index.table, "tabHD Ticket Comment")
+        self.assertEqual(index.column, "reference_ticket")
+
+
+# Table stats extracted using describe-database-table for testing.
+
+USER_TABLE = {
+    "table_name": "tabUser",
+    "total_rows": 92,
+    "schema": [
+        {
+            "column": "name",
+            "type": "varchar(140)",
+            "is_nullable": False,
+            "default": None,
+            "cardinality": 91,
+        },
+        {"column": "creation", "type": "datetime(6)", "is_nullable": True, "default": None},
+        {
+            "column": "modified",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 91,
+        },
+        {
+            "column": "modified_by",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "owner", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {"column": "docstatus", "type": "int(1)", "is_nullable": False, "default": "0"},
+        {"column": "idx", "type": "int(8)", "is_nullable": False, "default": "0"},
+        {"column": "enabled", "type": "int(1)", "is_nullable": False, "default": "1"},
+        {"column": "email", "type": "varchar(140)", "is_nullable": False, "default": ""},
+        {
+            "column": "first_name",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 88,
+        },
+        {
+            "column": "reset_password_key",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 84,
+        },
+        {
+            "column": "user_type",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": "System User",
+            "cardinality": 2,
+        },
+        {
+            "column": "api_key",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 70,
+        },
+        {"column": "api_secret", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_user_tags", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_comments", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_assign", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_liked_by", "type": "text", "is_nullable": True, "default": None},
+    ],
+    "indexes": [
+        {
+            "unique": True,
+            "cardinality": 91,
+            "name": "PRIMARY",
+            "sequence": 1,
+            "nullable": False,
+            "column": "name",
+            "type": "BTREE",
+        },
+        {
+            "unique": True,
+            "cardinality": 91,
+            "name": "username",
+            "sequence": 1,
+            "nullable": True,
+            "column": "username",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 91,
+            "name": "modified",
+            "sequence": 1,
+            "nullable": True,
+            "column": "modified",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 91,
+            "name": "reset_password_key_index",
+            "sequence": 1,
+            "nullable": True,
+            "column": "reset_password_key",
+            "type": "BTREE",
+        },
+    ],
+}
+
+
+HAS_ROLE_TABLE = {
+    "table_name": "tabHas Role",
+    "total_rows": 96,
+    "schema": [
+        {
+            "column": "name",
+            "type": "varchar(140)",
+            "is_nullable": "NO",
+            "default": None,
+            "cardinality": 92,
+        },
+        {"column": "creation", "type": "datetime(6)", "is_nullable": "YES", "default": None},
+        {"column": "modified", "type": "datetime(6)", "is_nullable": "YES", "default": None},
+        {
+            "column": "modified_by",
+            "type": "varchar(140)",
+            "is_nullable": "YES",
+            "default": None,
+        },
+        {"column": "owner", "type": "varchar(140)", "is_nullable": "YES", "default": None},
+        {"column": "docstatus", "type": "int(1)", "is_nullable": "NO", "default": "0"},
+        {"column": "idx", "type": "int(8)", "is_nullable": "NO", "default": "0"},
+        {
+            "column": "role",
+            "type": "varchar(140)",
+            "is_nullable": "YES",
+            "default": None,
+            "cardinality": 78,
+        },
+        {
+            "column": "parent",
+            "type": "varchar(140)",
+            "is_nullable": "YES",
+            "default": None,
+            "cardinality": 92,
+        },
+        {
+            "column": "parentfield",
+            "type": "varchar(140)",
+            "is_nullable": "YES",
+            "default": None,
+        },
+        {
+            "column": "parenttype",
+            "type": "varchar(140)",
+            "is_nullable": "YES",
+            "default": None,
+        },
+    ],
+    "indexes": [
+        {
+            "unique": True,
+            "cardinality": 92,
+            "name": "PRIMARY",
+            "sequence": 1,
+            "nullable": "",
+            "column": "name",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 92,
+            "name": "parent",
+            "sequence": 1,
+            "nullable": "YES",
+            "column": "parent",
+            "type": "BTREE",
+        },
+    ],
+}
+
+
+HD_TICKET_TABLE = {
+    "table_name": "tabHD Ticket",
+    "total_rows": 3820,
+    "schema": [
+        {
+            "column": "name",
+            "type": "bigint(20)",
+            "is_nullable": False,
+            "default": None,
+            "cardinality": 3529,
+        },
+        {"column": "creation", "type": "datetime(6)", "is_nullable": True, "default": None},
+        {
+            "column": "modified",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 3529,
+        },
+        {
+            "column": "modified_by",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "owner", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {"column": "docstatus", "type": "int(1)", "is_nullable": False, "default": "0"},
+        {"column": "idx", "type": "int(8)", "is_nullable": False, "default": "0"},
+        {"column": "subject", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {"column": "raised_by", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {
+            "column": "status",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": "Open",
+            "cardinality": 8,
+        },
+        {"column": "priority", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {
+            "column": "ticket_type",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "agent_group",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": "L1",
+            "cardinality": 9,
+        },
+        {
+            "column": "ticket_split_from",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "description", "type": "longtext", "is_nullable": True, "default": None},
+        {"column": "template", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {"column": "sla", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {
+            "column": "response_by",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "response_by_variance",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "agreement_status",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "resolution_by",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "resolution_by_variance",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "service_level_agreement_creation",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "on_hold_since",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "total_hold_time",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "first_response_time",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "first_responded_on",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "avg_response_time",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "resolution_details",
+            "type": "longtext",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "opening_date", "type": "date", "is_nullable": True, "default": None},
+        {"column": "opening_time", "type": "time(6)", "is_nullable": True, "default": None},
+        {
+            "column": "resolution_date",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "resolution_time",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {
+            "column": "user_resolution_time",
+            "type": "decimal(21,9)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "contact", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {"column": "customer", "type": "varchar(140)", "is_nullable": True, "default": None},
+        {
+            "column": "email_account",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "attachment", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_user_tags", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_comments", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_assign", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_liked_by", "type": "text", "is_nullable": True, "default": None},
+        {"column": "_seen", "type": "text", "is_nullable": True, "default": None},
+    ],
+    "indexes": [
+        {
+            "unique": True,
+            "cardinality": 3529,
+            "name": "PRIMARY",
+            "sequence": 1,
+            "nullable": False,
+            "column": "name",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 8,
+            "name": "status",
+            "sequence": 1,
+            "nullable": True,
+            "column": "status",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 3529,
+            "name": "modified",
+            "sequence": 1,
+            "nullable": True,
+            "column": "modified",
+            "type": "BTREE",
+        },
+    ],
+}
+
+
+HD_TICKET_COMMENT_TABLE = {
+    "table_name": "tabHD Ticket Comment",
+    "total_rows": 2683,
+    "schema": [
+        {
+            "column": "name",
+            "type": "varchar(140)",
+            "is_nullable": False,
+            "default": None,
+            "cardinality": 2683,
+        },
+        {"column": "creation", "type": "datetime(6)", "is_nullable": True, "default": None},
+        {
+            "column": "modified",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 2345,
+        },
+        {
+            "column": "reference_ticket",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 1379,
+        },
+        {
+            "column": "commented_by",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+        },
+        {"column": "content", "type": "longtext", "is_nullable": True, "default": None},
+        {"column": "is_pinned", "type": "int(1)", "is_nullable": False, "default": "0"},
+    ],
+    "indexes": [
+        {
+            "unique": True,
+            "cardinality": 2345,
+            "name": "PRIMARY",
+            "sequence": 1,
+            "nullable": False,
+            "column": "name",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 2345,
+            "name": "modified",
+            "sequence": 1,
+            "nullable": True,
+            "column": "modified",
+            "type": "BTREE",
+        },
+    ],
+}
+
+
+COMMUNICATION_TABLE = {
+    "table_name": "tabCommunication",
+    "total_rows": 20727,
+    "schema": [
+        {
+            "column": "name",
+            "type": "varchar(140)",
+            "is_nullable": False,
+            "default": None,
+            "cardinality": 19713,
+        },
+        {"column": "creation", "type": "datetime(6)", "is_nullable": True, "default": None},
+        {
+            "column": "modified",
+            "type": "datetime(6)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 19713,
+        },
+        {
+            "column": "reference_doctype",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 1,
+        },
+        {
+            "column": "reference_name",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 3798,
+        },
+        {
+            "column": "reference_owner",
+            "type": "varchar(140)",
+            "is_nullable": True,
+            "default": None,
+            "cardinality": 1314,
+        },
+    ],
+    "indexes": [
+        {
+            "unique": True,
+            "cardinality": 19713,
+            "name": "PRIMARY",
+            "sequence": 1,
+            "nullable": False,
+            "column": "name",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 19713,
+            "name": "modified",
+            "sequence": 1,
+            "nullable": True,
+            "column": "modified",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 2,
+            "name": "reference_doctype_reference_name_index",
+            "sequence": 1,
+            "nullable": True,
+            "column": "reference_doctype",
+            "type": "BTREE",
+        },
+        {
+            "unique": False,
+            "cardinality": 9856,
+            "name": "reference_doctype_reference_name_index",
+            "sequence": 2,
+            "nullable": True,
+            "column": "reference_name",
+            "type": "BTREE",
+        },
+    ],
+}
+
+
+EXPLAIN_OUTPUT = """[
+    {
+        "Extra": "",
+        "id": 1,
+        "key": "modified",
+        "key_len": "9",
+        "possible_keys": null,
+        "ref": null,
+        "rows": "20",
+        "select_type": "PRIMARY",
+        "table": "tabHD Ticket",
+        "type": "index"
+    },
+    {
+        "Extra": "Using index condition; Using where",
+        "id": 4,
+        "key": "reference_doctype_reference_name_index",
+        "key_len": "563",
+        "possible_keys": "reference_doctype_reference_name_index",
+        "ref": "const",
+        "rows": "10236",
+        "select_type": "DEPENDENT SUBQUERY",
+        "table": "tabCommunication",
+        "type": "ref"
+    },
+    {
+        "Extra": "Using index condition; Using where",
+        "id": 3,
+        "key": "reference_doctype_reference_name_index",
+        "key_len": "563",
+        "possible_keys": "reference_doctype_reference_name_index",
+        "ref": "const",
+        "rows": "10236",
+        "select_type": "DEPENDENT SUBQUERY",
+        "table": "tabCommunication",
+        "type": "ref"
+    },
+    {
+        "Extra": "Using where; Using index",
+        "id": 2,
+        "key": "reference_ticket_index",
+        "key_len": "563",
+        "possible_keys": "reference_ticket_index",
+        "ref": null,
+        "rows": "2823",
+        "select_type": "DEPENDENT SUBQUERY",
+        "table": "tabHD Ticket Comment",
+        "type": "index"
+    }
+]"""