SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f1eb757d7558eb1bd2aeb12b2b568841f992af514257ce86f0dc5801594e7ac' 
  AND token = 'HsOch5RZvGW1PM+CJTlu8CDkhMo1iyX8YvPUKSPZm+I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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