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Sergio S.
Expert-Vetted

Sergio S.

Modernization Integration Expert: Mainframe, Containers, Java, COBOL

Highly skilled systems architect and developer with more than 40 years of experience designing, developing, deploying and integrating applications, from old single platform “green-screen” to multi-tier / distributed systems. Business experience in manufacturing, accounting, distributing, payroll, finance and TELCO: ✔ Strong knowledge of Java SE and JEE stacks, from early versions 1.x up to latest version SE 17 and JEE 10 including Spring and Spring Boot. ✔ Deep understanding of old technologies such COBOL, VSAM, JCL, IMS, DB2, IMS “green screen”, etc. This knowledge allowed me to design, code and implement integrations between new applications with legacy ones. ✔ Solid leading and mentoring skills to help and encourage individuals to maximize their productivity by applying the best practices, frameworks, libraries and technology in general. ✔ I'm always learning about new technologies and tools to ease and reduce time spent in application development and deployment. Technology by itself is worth nothing if it does not solve real world problems.

🇬🇹Guatemala, Guatemala$60/hr100% JSS4.99 (35)Since Dec 2012

Earnings and projects

MRR
$8.8k

Last 6 months ÷ 6

World#1,729 / 412k
🇬🇹Country#1 / 369
Revenue, last 30 days
$8.8k

Last 6 months: $53k

World#1,889 / 412k
🇬🇹Country#2 / 369
Total earnings
$600k

Billed in all: $623k

World#1,866 / 412k
🇬🇹Country#2 / 369
Per project
$10k

$26k in the last 6 months

World#15,274 / 412k
🇬🇹Country#41 / 369
Projects, last 6 months
2
0% fixed100% hourly
World#88,918 / 412k
🇬🇹Country#56 / 369
Projects in all
58

Across 76 contracts

34% fixed66% hourly
World#52,574 / 412k
🇬🇹Country#24 / 369

Earnings, last 30 days

$623k+$8.8k earned in the last 30 daysBilled in all, before Upwork's fee · drag across the chart to see what was earned in any stretch
$610k$615k$620k$625kOct 8Oct 23Nov 7

Skill rankings: Top 0.57% in MySQL

Top 1% in 6 of 11 skills, ranked by MRR among everyone on Upwork with the skill.

  1. 3COBOL51 freelancers · 🇬🇹 #1Top 6%
  2. #5Relational Database218 freelancers · 🇬🇹 #1Top 2%
  3. #7Database Administration797 freelancers · 🇬🇹 #1Top 0.88%
  4. #15Spring Framework880 freelancers · 🇬🇹 #1Top 2%
  5. #16System Administration1,828 freelancers · 🇬🇹 #1Top 0.88%
  6. #22Database Design2,161 freelancers · 🇬🇹 #1Top 1%
  7. #39Kubernetes3,351 freelancers · 🇬🇹 #1Top 1%
  8. #41Angular6,816 freelancers · 🇬🇹 #1Top 0.60%