SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc594c8d47d720efb56152d18e6a61054aee45514816c5611d3de30677be6c03' 
  AND token = 'Hn6prV2TosOmMODHcYIvWtRctYPjKOxrMsghJ0/jDUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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