View log and you should see that the server is started very fast in milliseconds. In this case the default server was started in 0.403 seconds instead of several seconds if the application image doesn't have checkpoint.
kubectl -n $APP_NS logs getting-started-instanton-6866c57ff9-wt8xm
Found mounted TLS certificates, generating keystore
Found mounted TLS CA certificate, adding to truststore
[3/9/23, 16:38:19:757 UTC] 0000002e com.ibm.ws.app.manager.AppMessageHelper A CWWKZ0001I: Application guide-getting-started started in 0.173 seconds.
[3/9/23, 16:38:19:777 UTC] 0000002e com.ibm.ws.config.xml.internal.ConfigRefresher A CWWKG0016I: Starting server configuration update.
[3/9/23, 16:38:19:778 UTC] 0000002e com.ibm.ws.config.xml.internal.ServerXMLConfiguration A CWWKG0093A: Processing configuration drop-ins resource: /opt/ol/wlp/usr/servers/defaultServer/configDropins/defaults/checkpoint.xml
[3/9/23, 16:38:19:778 UTC] 0000002e com.ibm.ws.config.xml.internal.ServerXMLConfiguration A CWWKG0093A: Processing configuration drop-ins resource: /opt/ol/wlp/usr/servers/defaultServer/configDropins/defaults/keystore.xml
[3/9/23, 16:38:19:779 UTC] 0000002e com.ibm.ws.config.xml.internal.ServerXMLConfiguration A CWWKG0093A: Processing configuration drop-ins resource: /opt/ol/wlp/usr/servers/defaultServer/configDropins/defaults/open-default-port.xml
[3/9/23, 16:38:19:781 UTC] 0000002e com.ibm.ws.config.xml.internal.ServerXMLConfiguration A CWWKG0093A: Processing configuration drop-ins resource: /opt/ol/wlp/usr/servers/defaultServer/configDropins/overrides/truststore.xml
[3/9/23, 16:38:19:866 UTC] 00000030 com.ibm.ws.config.xml.internal.ConfigRefresher A CWWKG0017I: The server configuration was successfully updated in 0.091 seconds.
[3/9/23, 16:38:19:929 UTC] 0000002e io.openliberty.checkpoint.internal.CheckpointImpl A CWWKC0452I: The Liberty server process resumed operation from a checkpoint in 0.346 seconds.
[3/9/23, 16:38:19:931 UTC] 0000002e com.ibm.ws.tcpchannel.internal.TCPPort I CWWKO0219I: TCP Channel defaultHttpEndpoint has been started and is now listening for requests on host * (IPv6) port 9080.
[3/9/23, 16:38:19:956 UTC] 0000002e com.ibm.ws.kernel.feature.internal.FeatureManager A CWWKF0012I: The server installed the following features: [cdi-3.0, checkpoint-1.0, concurrent-2.0, distributedMap-1.0, jndi-1.0, json-1.0, jsonb-2.0, jsonp-2.0, monitor-1.0, mpConfig-3.0, mpHealth-4.0, mpMetrics-4.0, restfulWS-3.0, restfulWSClient-3.0, servlet-5.0, ssl-1.0, transportSecurity-1.0].
[3/9/23, 16:38:19:983 UTC] 0000002e com.ibm.ws.kernel.feature.internal.FeatureManager I CWWKF0008I: Feature update completed in 0.400 seconds.
[3/9/23, 16:38:19:987 UTC] 0000002e com.ibm.ws.kernel.feature.internal.FeatureManager A CWWKF0011I: The defaultServer server is ready to run a smarter planet. The defaultServer server started in 0.403 seconds.
[3/9/23, 16:38:19:990 UTC] 00000038 com.ibm.ws.security.token.ltpa.internal.LTPAKeyCreateTask I CWWKS4105I: LTPA configuration is ready after 0.136 seconds.
[3/9/23, 16:38:20:158 UTC] 0000002a com.ibm.ws.ssl.config.WSKeyStore I Successfully loaded default keystore: /opt/ol/wlp/output/defaultServer/resources/security/key.p12 of type: PKCS12
[3/9/23, 16:38:20:179 UTC] 00000044 com.ibm.ws.tcpchannel.internal.TCPPort I CWWKO0219I: TCP Channel defaultHttpEndpoint-ssl has been started and is now listening for requests on host * (IPv6) port 9443.