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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7ce48fb50c00a5400fb675e5c2d56c29da50845afe9304d97b1d124c792fec5' 
  AND token = 'zlbHrZLtb2bucwqxheqGej+vjYr+vlOUzNdh+XXdSVo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}