SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'db1bc50e6eb03a2c4dbb7537b03215e96e480d7df30a609c28694b056694c569' 
  AND token = 'FBbqpVJhbm9fNfOoKz8WA/FDGdcRciNUKToyWiA0X88=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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