SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d40afff679dc7431d4f17aa1398b6b967465a62a2e67f76b78d132c2903fef3' 
  AND token = '/mBMCAqKcf/+jU29VM5lLHe7PO2D/EWXIZSWwx11pzA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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