SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '58686e42d385c880166283df634029cfc48684a69fd3bd687578893c7eebb378' 
  AND token = '+7zHPxDrRfthHuYzQFWsPRk9l/T2pAg/ORVncp7v2qo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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