SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '684f3c4daee661678d7c767a8b176e542fe3a9d4960a69d44c0281c2e29ede41' 
  AND token = 'pZw7uxbQweQCoRpmCYeCSWlsmbbgDOFXZUEIf8khGnQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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