SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'aa4990d49c2549fe644eb258100668d1c0da7d99d71da5f1f86e2af7fd459807' 
  AND token = 'PYuAjWRza9neft3FUEei3nBfoMpgpIQaAugMF5Ommdg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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