SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f997ad5207e8090d53a4800da11603e6732344faa536b38ec82757391039d7a' 
  AND token = 'nxHCjb5hvOjxqC/6IwrPDZp4HxoIq+j8WGko+QMGuPA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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