SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a71d6b61652164a28de93088d3bb5737af550ce626db96c2f7efe8476fee9500' 
  AND token = 'fkXRs0CruUn/ghearydhwyIIbUBWcjXnNTM7WeNZc0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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