SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'acc4fd7b1a4ff111cf688022b945237e56112f541dc868727475ac8acdad5e6d' 
  AND token = 'ANvQFIbL2OdNCJ8dwlAmzzgGTz/ewXToBneuoWxWHLs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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