SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f0ee560319304cfbf82091696c24cfb71beaff2eabd450ab4be34a75433a1f5' 
  AND token = 'b6FWtWjINdzJapxE9T+jtaZ9YRUOZsh3FYBVdIKaRQw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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