In your situation, PostgreSQL seems to be better option. Why? 1) Saving structured data is possible in both PostgreSQL and Elasticsearch. In PostgreSQL, there is JSONB column available and you can build indexes on top of it. 2) If you are able to specify the time as a primary key, both Elasticsearch and PostgreSQL are great options. 3) PostgreSQL allows you to do a lot more with your data and handle them in a relation way. You are not clear whether it's a benefit or not but let's consider extensibility to be an advantage. 4) PostgreSQL comes with PostGIS extension to work with geo data. May be useful for your situation. 5) PostgreSQL may serve for other needs of your app. Managing one database is always better than having two of them.

Thanks to JSONB column type, PostgreSQL is a sweet combination of relational and noSQL database, but there are also drawbacks coming from ACID compliancy and WAL overhead for rapid changes.