SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7f9eb6542bd1988a2472d75c080dfff203ec2915d92eab581d7cf25863736d5e' 
  AND token = 'MRTVXfFYl+Z00rW/wRgI9hVmMrKfnSbXE/Z3OWB2PQQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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