SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db58d03016f5df50239050690c107014f6884d3075193438be95012cf49895fa' 
  AND token = 'ONRnYvGcjn1BNXd+H5feG5TEi+gXmjBIGZt+nX6scUQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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