SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4a921b355cff3ba3f7e483b2ee149b4438a026f9230b05add0c0c8c182f8c909' 
  AND token = 'WTeX7aO1j6El8V2h2hPe1sQfgeITrcXsVtJ1u9HN4lY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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