SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52e731ef6bce6555fe393b9ebb620e0f245c14368dc2ba21bda4e1902d626b88' 
  AND token = 'KZXl6cCAxNmGGhviWGdmfZi+rVDvjEfpzml6sqMwIMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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