SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2e35aa91dd040bc6d6e34177ae4b6d50606703353cd30e56bfa9310938da0a50' 
  AND token = 's/tEzqvNTur7DhGlGIbqx6LQzixvMXtAigHubNVE3Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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