SQL query to check the count

I have a column in bigquery which is time in the below format. The time(time is in utc) increases in 15 minute interval(starting from 00:10) and it continues for the whole day till 23:.....

00:10   
00:25   
00:40   
...

now i want to check if we have data uptodate using a query. That is every time point we should have multiple entries(count should be >0 when grouped by time). If there is no count at a particular point my query should be returning a flag whih raises that.
if we are running the query at 01:05 we know that there should be four points(00:10 00:25 00:40 00:55) with non zero count
How do we compare and ensure this using a query?

select timecolumn as time, count(*) as cnt 
from 'project.dataset.table' 
group by 1 
order by 1 

will give the below

00:10     5 
00:25     5
00:40     10

....



select timecolumn as time, count(*) as cnt 
from 'project.dataset.table'

I believe you can skip group by and do something like shown below.

Number of rows returned by required_times will grow from 0 to a max of 24*4 records during the day.

my_data_table is just for emulating your data table. You may need to apply timestamp_trunc(timecolumn, MINUTE) for your data if it does not match exactly with values from required_times.

with required_times as (
  select * from unnest(GENERATE_TIMESTAMP_ARRAY(
    date_add(timestamp_trunc(current_timestamp(), DAY), INTERVAL 10 MINUTE), 
    current_timestamp(), 
    INTERVAL 15 MINUTE)) as timecolumn
),
my_data_table as (
  select * from unnest(GENERATE_TIMESTAMP_ARRAY(
    date_add(timestamp_trunc(current_timestamp(), DAy), INTERVAL 10 MINUTE), 
    date_add(current_timestamp(), INTERVAL -1 HOUR), 
    INTERVAL 15 MINUTE)) as timecolumn
)

select
  required_times.timecolumn
from
  required_times
  left join my_data_table on required_times.timecolumn = my_data_table.timecolumn
where
  my_data_table.timecolumn is null 

will return e.g. like this because records for the last hour of day is missing from my_data_table