SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b688582dcc1d21936c564c75a03c8394116d181966c8b68faeaa08f098e9ca1' 
  AND token = 'gZ0jFCF9qBs+mv3s8ZWKlMVlEjDDQwzRxmd0HM5GXYk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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