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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '138b7d2bdc1320a38c4db94672beb74890b1cee0a738cc8df0f0c8b40b35b889' 
  AND token = '5CQR4fmwafFLqppRVDwnxjusLhPwH5txGcQvTQtC35Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}