SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '828b81a52858dd9bbbf8dc212f1babc2e0291a2b59f3cc0ae39ee5b06b51c44c' 
  AND token = '1QY8xro99xDPvrTrR17dhrHOfUvqNSNcwDYMzTT+u4g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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