SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68da74ba35bd9f5ee68c275ca6d50788f369559a65ef9a74ca3588626cc82b21' 
  AND token = 'u3MVtyJMOa+I957NWaZd9omzIJiP4UZiXpeuBMSTuR8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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