SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '820f904d05547ee0a2167142be6cbcef6f4de7002323e4d11d552a100610fff8' 
  AND token = '0NMfdDHlNT/bXqjF/BsIUNd7bGSwwDwvHaRUN+zVZUU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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