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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6c08382117a71765d6fe8b22376fd44d885c0c4a6bb74da56de341a9f28f07b' 
  AND token = 'tp1bDz7t3/jqZPo7tDAJ+t/+RtTlCbH7aHhWU3rUDaQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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