Schema for will/datascope using free data tier heroku postgres database. The trigger will keep the last 10000 elements

schema.sql

CREATE TABLE stats (id serial primary key, created_at timestamptz default (now()), data json);
create index ON stats (created_at);

-- Function that will delete old rows to keep the size of the set to 10_000 rows
CREATE OR REPLACE FUNCTION prune_stats_table()
RETURNS trigger AS
$BODY$
BEGIN
  DELETE FROM stats WHERE id < (SELECT id FROM stats ORDER BY id DESC LIMIT 1 OFFSET 9999);
  return null;
END
$BODY$
LANGUAGE plpgsql;

-- Trigger pruning before each update... slow but do the job
CREATE TRIGGER prune_stats_trigger
AFTER INSERT OR UPDATE
ON stats
EXECUTE PROCEDURE prune_stats_table();