SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3e51f76538021d411af9c5461faeb529bbe243bfeaf18f175d35b3523390831b' 
  AND token = '7SrKRAaXvNTNI7vPZVnQ/FMmeqA968UCl8K7OmI7KxM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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