SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f9128a1b31ef45df528fec78ff2c66d9d660f8d6f892405be557220b1c88cb68' 
  AND token = 'KproQDD2iIoekj1O+ThERl1JNo/VNtBNy/FJB9siaC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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