SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a543f06fc80e133de14885565530cd38df815aff5cccbd28c13c3a53a37f5953' 
  AND token = 'PVcp94n3SSpHnu6FUOTeuVPhCilj+ZqhAsMl8AOc0G0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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