SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f3149ab95bf364935fe3277003433cb5a92396b0b4228527e07de7652801f97' 
  AND token = 'Yn3WwPmKNMj9MXoMOBgZd3dFGKHYHlFGDWGX1ao+YP0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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