SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b6b3233f0741eb2d848e82f949769832387e357b9324c561131a99061b6ced8' 
  AND token = '1uWp0liyplFEFVWdeTUf/iJuxi5ABGEkOGUMCiU/srE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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