Query optimisation in SQL Server - sql-server

Question

The following is taking a long time to get executed. Considering each table has close to 50 million to 100 million rows, is there anything that I can do from the query side to get it optimized.It is a source table and involves huge data movements (insertion ranging in millions) every hour and is better off without indexes.I don't have the required access to get an execution plan from this server.
DECLARE #var INT
SELECT TOP 1 #var = s_type
FROM s_shot
WHERE s_type < 10000
ORDER BY s_type DESC;
WITH cte AS
(
SELECT
sps_id,
SUM(xin) xin,
SUM(xout) xout
FROM
s_lock
GROUP BY
sps_id
)
SELECT
A.[s_id], a.acc_id,
B.[o_type],
B.[o_id], B.[sec_id], B.[c_id],
B.[style_type_id], [s_type],
A.[end_date],
B.[mv],
b.xin + ISNULL(c.xin, 0) [xin],
b.xout + ISNULL(c.[xout], 0) xout,
b.accr_in + b.accr_inter [acc],
b.accr_in, b.accr_inter,
b.units
FROM
s_shot a WITH (NOLOCK)
JOIN
s_pos3 b WITH (NOLOCK) ON a.s_id = b.s_id
JOIN
cte c ON b.sps_id = c.sps_id
WHERE
b.is_sl = 1
AND a.end_date > DATEADD(mm, -24, GETDATE()) -- 24 months
As you can see, I want to fetch the data of last 24 months. Is there any optimization that is possible in this query so as to bring down its execution time to manageable levels.
The create table scripts are provided below.
CREATE TABLE [dbo].[s_shot]
(
[s_id] [int] IDENTITY(1,1) NOT NULL,
[acc_id] [int] NULL,
[s_type] [int] NULL,
[end_date] [datetime] NULL,
[recon] [tinyint] NULL,
[is_pers] [tinyint] NOT NULL,
CONSTRAINT [PK_s_shot_1] PRIMARY KEY NONCLUSTERED
(
[s_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
CREATE TABLE [dbo].[s_lock]
(
[sps_id] [int] NOT NULL,
[units] [decimal](18, 5) NULL,
[accr_in] [decimal](18, 2) NULL,
[xin] [decimal](18, 2) NULL,
[xout] [decimal](18, 2) NULL,
[lock_date] [date] NOT NULL,
[accr_inter] [decimal](18, 2) NULL,
[mv] [decimal](18, 2) NULL,
CONSTRAINT [PK_s_lock] PRIMARY KEY CLUSTERED
(
[sps_id] ASC,
[lock_date] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
CREATE TABLE [dbo].[s_pos3]
(
[sps_id] [int] IDENTITY(1,1) NOT NULL,
[s_id] [int] NOT NULL,
[o_type] [tinyint] NOT NULL,
[o_id] [int] NOT NULL,
[s_id] [int] NOT NULL,
[c_id] [int] NOT NULL,
[s_type_id] [int] NOT NULL,
[units] [decimal](18, 5) NULL,
[accr_income] [decimal](18, 2) NULL,
[distr] [decimal](18, 2) NULL,
[mv] [decimal](18, 2) NULL,
[perf_stat] [smallint] NULL,
[is_slv] [bit] NULL,
[accr_inter] [decimal](18, 2) NULL,
[perf_mtd] [decimal](18, 10) NULL,
[xin] [decimal](18, 2) NULL,
[xout] [decimal](18, 2) NULL,
[a_s_type_id] [int] NULL,
CONSTRAINT [PK_s_pos3] PRIMARY KEY NONCLUSTERED
(
[sps_id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]
Any help is appreciated.
Edit: Updated indexing details