SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f88e84aab24937526e620e301886fbba08879f63521b25ec882a2ca9b566950f' 
  AND token = '34/Z/UkTks8phi8DiVaCw6uhvIWXrC8M5RNxoSaUwcM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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