SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'db0f1372ff481efa26aa509bfe7fce11f188ad42196f480b829d515d38b0f434' 
  AND token = 'rEpVlqfslZSVrYG8hMbshKUrgRXUTb8Ls4DdbHKisYM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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