SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9407f52499edc6065743eced5cbb5e146de16b0aa79ae8d91eee33256368a819' 
  AND token = 'K70RTU7HVWsrM5AMScrTvPXMBc7GQGAwzESNU++eORs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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