SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ae0408ed9dfbad73a8eb2aab8675a6283e481a959be5acb3d6a7338fac122fdd' 
  AND token = 'f/MqZWPjxDKWcz2VE0ZrbxjxntIJDgEEa9nIDBzI4uk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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