SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f8c135b4fdae033c398d00b12e59f48836ed31b572718ec001f1cf4cb72eb78' 
  AND token = 'XccliNuboiyRiFSvQucW7IrqdYxdsSj4JcBVAyQllmc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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