SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42395096f4c085aae4180643d8436f11689681783af79bcaefae2f3e88656f9d' 
  AND token = '/DC2gviudFk3A2GvSPmcpMKifkp0XkNzIxzAIYe9k6o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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