Hikari CP connections are suddenly invalidated - postgresql

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Hi Stackoverflow family,
So we have an application with Kotlin & Spring boot that uses a single DB instance(1 GB Memory and instance class is db.t3.micro) as PostgreSQL and is hosted in AWS. What happens for the last couple of days is suddenly connections in my pool are invalidated(2-3 times a day) and the pool size drops drastically. In summary:
Let's say everything is normal in Hikari and the connections are closed and added according to the maxliftime which is 30 minutes by default and the log are like below:
HikariPool-1 - Pool stats (total=40, active=0, idle=40, waiting=0)
HikariPool-1 - Fill pool skipped, pool is at sufficient level.
Suddenly most of the connections become invalidated. Let's say 30 out of 40. The connections are closed before they pass their max lifetime and the logs are like below for all closed connections:
HikariPool-1 - Failed to validate connection org.postgresql.jdbc.PgConnection#5257d7b2 (This connection has been closed.). Possibly consider using a shorter maxLifetime value.
HikariPool-1 - Closing connection org.postgresql.jdbc.PgConnection#7b673105: (connection is dead)
Additionally after these messages followed by multiple of this logs like below:
Add connection elided, waiting 6, queue 13
And the timeout failure stats like below:
HikariPool-1 - Timeout failure stats (total=12, active=12, idle=0, waiting=51)
Finally, I have left with lots of connection timeouts of requests due to the reason that there were no connection available for the most of the requests:
java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30000ms
I have added leak-detection-threshold and it also logs like below during the problem happening:
Connection leak detection triggered for org.postgresql.jdbc.PgConnection#3bb5f155 on thread http-nio-8080-exec-482, stack trace follows
java.lang.Exception: Apparent connection leak detected
The hikari config is like below:
hikari:
data-source-properties: stringtype=unspecified
maximum-pool-size: 40
leak-detection-threshold: 30000
When this problem happens queries in PostgreSQL also take a lot of time: 8-9 seconds and increase up to 15-35 seconds. Some queries even 55-65 seconds(which usually take 1-3 seconds at most in usual times). That is why we think it is not a query issue.
In addition to that some sources suggest using try with resources, however, it is not the case for us as we do not obtain connections manually. In addition to that increasing the max pool size from 20 to 40 also did not help. I would really appreciate any comment or hint as we are dealing with this issue for almost a week.