SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '338ba8b943e5e5aedb564e84542c8c7095b4fd6603ae9cc6b20425f2305590cb' 
  AND token = '5D0f15Tu522wvpshQ6PsHCbuXIvqV205RjhBSyIjDsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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