SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7242803de1c4a67590e3f10baa22c342e162c178b77af2776c1eef134457922d' 
  AND token = '6J6ebyfHCvby6+aYt6D8hcQ6e9zCDsTloGYuLqkt3wk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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