SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '347b600fd6ce1cd7bff49994b84d46958af221c24931900738f540655993a15a' 
  AND token = 'Yj/m+w4YMoPeD4wdxIO4RbNEzrKlmEQVpl7Kubx2HU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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