SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '67d2d8a6bbeae2572264149f1e3dadb2c8d73a556f88653c634d4b351841a2d7' 
  AND token = 'raU722LMuwGgWZAlgRbFQQgIRRpE+xEahqsUJQrISVU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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