SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf408bbc44861e2756341ac7076a6da16d63fd553ffc23953ffb6b582af94cad' 
  AND token = 'l9e8XwJzYrDmNGiihS8K4AxwBCXhiW+yP9QKCLp4zT4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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