SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6908c80019c716fd211e750075145fff51be9219d6338cb179397ad7c7f7ed3' 
  AND token = 'xEsiiPmfZCNwq785/raIleDPgv3xPBjBQ7svIMy8sRg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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