Some requests fail with error "database is locked"

From the server logs:

May 07 15:56:23 ...: "onException"
May 07 15:56:23 ...: SQLite3 returned ErrorBusy while attempting to perform prepare "CREATE TABLE IF NOT EXISTS vouchers (id INTEGER PRIMARY KEY, name TEXT UNIQUE)": database is locked
May 07 15:56:23 ...: "onException"
May 07 15:56:23 ...: SQLite3 returned ErrorBusy while attempting to perform prepare "CREATE TABLE IF NOT EXISTS vouchers (id INTEGER PRIMARY KEY, name TEXT UNIQUE)": database is locked

It's not clear what endpoint these requests are for. They seem to come in pairs so a good guess might be that they are the /v1/redeem endpoint from a client with a few unredeemed vouchers which is periodically retrying redemption.