SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '18b58a8876363a386f12d4f873285a1b34f222519760b114d3aca9883459ff95' 
  AND token = 'vimT6OpXzPfPVFdc+yO1tBBRl+vvbKpQkZtDc5FHQic=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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