SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ef4653a516b5d024590da43ffbe56c86e91f0062cfbba0aca6326b425a350f' 
  AND token = 'vRzPGnvfcLuC4UI1aeNWyNSjnAEU9w3DtMH4PnSi2+c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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