SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b6ed54df654f5d4cf724599c69508fd0573e902eb8e277afafe58878d2d33ea' 
  AND token = 'OLFu+c3ZjzBRRC7r5bje6/2q2WrlGOgaw3bL7k3+hTg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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