SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e2f438ed41f58497a50e998cc4a2506e270fe9a0958d5eb7b4bc41ef8bda2b3' 
  AND token = 'i/LtDc5UjLsHX7dSOKjpq3XqTv3uhvyQpV4h9Bq4ioA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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