public class LambdaApp implements RequestHandler<String, Object>
{
    private static final Logger LOGGER = LoggerFactory.getLogger(LambdaApp.class);
    private static final Logger SPLUNK_LOGGER = LoggerFactory.getLogger("splunk.logger");

    @Override
    public Object handleRequest(String event, Context context)
    {

        SPLUNK_LOGGER.info("AWS Lambda start");
        try {
            Thread.sleep(50000);
        } catch(InterruptedException ex) {
            Thread.currentThread().interrupt();
        }
        return "handled";
    }

<dependency>
         <groupId>com.splunk.logging</groupId>
         <artifactId>splunk-library-javalogging</artifactId>
         <version>1.5.2</version>
</dependency>

<appender name="http" class="com.splunk.logging.HttpEventCollectorLogbackAppender">
    <url>https://a.b.c.d:8088</url>
    <token>valid-token</token>
    <disableCertificateValidation>true</disableCertificateValidation>
    <layout class="ch.qos.logback.classic.PatternLayout">
        <pattern>{%msg}</pattern>
    </layout>
</appender>

<logger name ="splunk.logger" level="DEBUG">
      <appender-ref ref="http" />
   </logger>