SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c55a9a852eba5bc7c630f694eca43fc63ebfec0868683272dbbfa0ea2d2f75ae' 
  AND token = 'R2M9MV6DsybNZD8btlMjmioivwLELeE+LFUK4kJO47o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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