Messages about parallel redo

Parallel redo is shutdown for database '' with worker pool size . Parallel redo is started for database '' with worker pool size . Starting up database '' I see this on a client PC a lot in the Windows Event Viewer (Event Id 49930 or 17137). This is a regular Windows PC, not a server, with a default instance of SQL Server 2017 Express Edition and SSMS. What is that parallel redo? Here's the output from the error log:

2019-05-28 12:23:03.360	spid16s	A self-generated certificate was successfully loaded for encryption.
2019-05-28 12:23:03.360	spid16s	Server is listening on [ 'any'  1433].
2019-05-28 12:23:03.360	spid16s	Server is listening on [ 'any'  1433].
2019-05-28 12:23:03.360	spid16s	Server is listening on [ 'any'  50374].
2019-05-28 12:23:03.360	spid16s	Server is listening on [ 'any'  50374].
2019-05-28 12:23:03.360	spid16s	Server local connection provider is ready to accept connection on [ \\.\pipe\SQLLocal\FOLLOWIN ].
2019-05-28 12:23:03.360	spid16s	Server named pipe provider is ready to accept connection on [ \\.\pipe\MSSQL$FOLLOWIN\sql\query ].
2019-05-28 12:23:03.360	spid16s	Dedicated administrator connection support was not started because it is disabled on this edition of SQL Server. If you want to use a dedicated administrator connection, restart SQL Server using the trace flag 7806. This is an informational message only. No user action is required.
2019-05-28 12:23:03.360	Server	SQL Server is attempting to register a Service Principal Name (SPN) for the SQL Server service. Kerberos authentication will not be possible until a SPN is registered for the SQL Server service. This is an informational message. No user action is required.
2019-05-28 12:23:03.360	spid16s	SQL Server is now ready for client connections. This is an informational message; no user action is required.
2019-05-28 12:23:03.370	Server	The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/pcFoo:FOLLOWIN ] for the SQL Server service. Windows return code: 0xffffffff, state: 63. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.
2019-05-28 12:23:03.370	Server	The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/pcFoo:1433 ] for the SQL Server service. Windows return code: 0xffffffff, state: 63. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.
2019-05-28 12:23:03.430	spid17s	A new instance of the full-text filter daemon host process has been successfully started.
2019-05-28 12:23:03.520	spid12s	Starting up database 'mssqlsystemresource'.
2019-05-28 12:23:03.520	spid21s	Starting up database 'Foobar'.
2019-05-28 12:23:03.520	spid20s	Starting up database 'msdb'.
2019-05-28 12:23:03.530	spid12s	The resource database build version is 14.00.3162. This is an informational message only. No user action is required.
2019-05-28 12:23:03.550	spid12s	Synchronize Database 'master' (1) with Resource Database.
2019-05-28 12:23:03.550	spid21s	Parallel redo is started for database 'Foobar' with worker pool size .
2019-05-28 12:23:03.560	spid12s	Starting up database 'model'.
2019-05-28 12:23:03.560	spid21s	Parallel redo is shutdown for database 'Foobar' with worker pool size .
2019-05-28 12:23:03.580	spid12s	Synchronize Database 'model' (3) with Resource Database.
2019-05-28 12:23:03.590	spid12s	Polybase feature disabled.
2019-05-28 12:23:03.590	spid12s	Clearing tempdb database.
2019-05-28 12:23:03.670	spid12s	Starting up database 'tempdb'.
2019-05-28 12:23:03.710	spid20s	Synchronize Database 'msdb' (4) with Resource Database.
2019-05-28 12:23:03.710	spid21s	Synchronize Database 'Foobar' (5) with Resource Database.
2019-05-28 12:23:03.710	spid22s	The Service Broker endpoint is in disabled or stopped state.
2019-05-28 12:23:03.710	spid22s	The Database Mirroring endpoint is in disabled or stopped state.
2019-05-28 12:23:03.730	spid22s	Service Broker manager has started.
2019-05-28 12:23:03.730	spid6s	Recovery is complete. This is an informational message only. No user action is required.
2019-05-28 12:28:21.180	spid51	Attempting to load library 'xplog70.dll' into memory. This is an informational message only. No user action is required.
2019-05-28 12:28:21.180	spid51	Using 'xplog70.dll' version '2017.140.3162' to execute extended stored procedure 'xp_msver'. This is an informational message only; no user action is required.
2019-05-28 12:28:21.320	spid51	Starting up database 'Foobar'.
2019-05-28 12:28:21.340	spid51	Parallel redo is started for database 'Foobar' with worker pool size .
2019-05-28 12:28:21.350	spid51	Parallel redo is shutdown for database 'Foobar' with worker pool size .
2019-05-28 12:28:21.360	spid51	Starting up database 'Foo'.
2019-05-28 12:28:21.380	spid51	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 12:28:21.400	spid51	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 12:28:21.410	spid51	Synchronize Database 'Foo' (6) with Resource Database.
2019-05-28 14:27:21.430	spid59	Starting up database 'Foo'.
2019-05-28 14:27:21.450	spid59	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:27:21.470	spid59	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:27:21.480	spid59	Starting up database 'Foobar'.
2019-05-28 14:27:21.500	spid59	Parallel redo is started for database 'Foobar' with worker pool size .
2019-05-28 14:27:21.510	spid59	Parallel redo is shutdown for database 'Foobar' with worker pool size .
2019-05-28 14:27:38.330	spid59	Starting up database 'Foobar'.
2019-05-28 14:27:38.360	spid59	Parallel redo is started for database 'Foobar' with worker pool size .
2019-05-28 14:27:38.370	spid59	Parallel redo is shutdown for database 'Foobar' with worker pool size .
2019-05-28 14:27:40.010	spid59	Starting up database 'Foo'.
2019-05-28 14:27:40.050	spid59	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:27:40.080	spid59	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:28:04.160	spid59	Starting up database 'Foo'.
2019-05-28 14:28:04.180	spid59	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:28:04.210	spid59	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:28:10.620	spid52	Attempting to load library 'xpstar.dll' into memory. This is an informational message only. No user action is required.
2019-05-28 14:28:10.690	spid52	Using 'xpstar.dll' version '2017.140.3162' to execute extended stored procedure 'xp_instance_regread'. This is an informational message only; no user action is required.
2019-05-28 14:28:14.220	spid52	Starting up database 'Foo'.
2019-05-28 14:28:14.240	spid52	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:28:14.270	spid52	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:28:14.410	Backup	Database backed up. Database: Foo, creation date(time): 2019/05/08(15:06:00), pages dumped: 2555, first LSN: 48:9778:37, last LSN: 48:9795:1, number of dump devices: 1, device information: (FILE=2, TYPE=DISK: {'C:\Users\Joe\Documents\Backup Followin\Foo_FULL_05272019_235209.BAK'}). This is an informational message only. No user action is required.
2019-05-28 14:28:14.420	Backup	BACKUP DATABASE successfully processed 2546 pages in 0.112 seconds (177.529 MB/sec).
2019-05-28 14:28:19.120	spid53	Starting up database 'Foo'.
2019-05-28 14:28:19.140	spid53	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:28:19.160	spid53	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:28:20.610	spid59	Starting up database 'Foo'.
2019-05-28 14:28:20.650	spid59	Parallel redo is started for database 'Foo' with worker pool size .
2019-05-28 14:28:20.670	spid59	Parallel redo is shutdown for database 'Foo' with worker pool size .
2019-05-28 14:28:31.030	spid54	Using 'dbghelp.dll' version '4.0.5'

0.3162.1 (X64)

May 15 2019 19:14:30

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Express Edition (64-bit) on Windows 10 Pro 10.0  (Build 17763: )