SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f5ca86b77443c7694d189efcad52549688754a8796ee86952b3fb0b7bc96f6f' 
  AND token = '9U0jupYiJ9IB5NaJxEAgYQ8zXcU+LmMZvNYF1NMzWPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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