SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b49f517c1d607030a79f320906a6d137534595c67bfe5f2ec6cd8d237cf613ba' 
  AND token = 'ISzcHFrDCK4QoIoFW+gicAq57gn055JbkTOzjFyBo38=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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