SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fe91fb482092f359bb15a0efad261db2f360450265604fdd1eec16177415d4a0' 
  AND token = 's+JSJlOtkv4S/oPvcqq/o+SGUyyE21JgItFWCdfDU00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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