SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3fdcff87fe5176271f744b3215f5ec2f58b93e76be3644d151e52bf90a5409c' 
  AND token = 'v8DlgiI/gin4o7VZs5VObzhOrZwQqnGhgSssVKheSeU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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