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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8998bfda91e36dd1acf75060f8b056067888c6d3481e2d610ff7670f4ee5d26' 
  AND token = 'psUeqp3zDHZE5NUKI1WWwZOOURbVc0ZLhPsZPOaCAWg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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