Query Optimization Required, PostgreSQL

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--PostgreSQL 9.6
--'\\' is a delimiter

drop table if exists Service cascade;

create table Service (user_id int,service_id varchar,created_at timestamp);
INSERT INTO Service
  ( user_id, service_id, created_at )
VALUES
  (201, 'rcygo', '2016-06-22 19:10:25-07'), 
  (32, 'qkbhX', '2016-07-08 06:07:25-07'), 
  (143, 'qmBr2', '2016-03-11 01:11:25-07'),
  (107, 'rcygo', '2017-11-29 21:09:19-07'),
  (32, 'sd4ifdca', '2017-03-22 19:10:25-07'), 
  (143, 'rcygn', '2016-04-08 06:07:25-07'), 
  (144, 'qbArm0', '2016-03-11 01:11:25-07'),
  (32, 'rbEkP', '2016-11-29 21:09:19-07'),
  (201, 'qkbhX', '2016-09-22 19:10:25-07'),
  (201, 'qkbhX', '2016-09-22 19:10:25-07'),
  (107, 'qmBr2', '2017-12-29 21:09:19-07'),
  (201, 'qmBr2', '2017-12-30 21:09:19-07');
;
SELECT CAST(count( distinct sr.user_id) as INT) as "Unique users Acquiring Entered Service",CAST(0 as TEXT) as "Other Services Acquired By These Unique Users",CAST(0 as INT) as "Total Unique Users of These Other Acquired Services"
from public.Service sr 
where sr.service_id='rcygo' --So this would be user entered field but for now i have populated it with a value
group by 2,3 
UNION
Select CAST(0 as INT) as "Unique users Acquiring Entered Service",CAST(B.Other_Services as TEXT) "Other Services Acquired By These Unique Users",CAST(count(distinct C.user) as INT) as "Total Unique Users of These Other Acquired Services" 
FROM 
(
SELECT sr.user_id as user 
from public.Service sr 
where sr.service_id='rcygo' --So this would be user entered field but for now i have populated it with a value
) As A 
JOIN 
(
SELECT sr.user_id as user,sr.service_id as Other_Services 
from public.Service sr 
where sr.service_id<>'rcygo' --So this would be user entered field but for now i have populated it with a value
) AS B 
on A.user=B.user
JOIN 
(
SELECT sr.user_id as user,sr.service_id as Other_Services 
from public.Service sr 
) AS C
on B.Other_Services=C.Other_Services 
group by 1,2
order by 1 desc,3 desc
LIMIT 8


absolute service time: 0,47 sec