SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '17b27cd31b9487a064bc8ff98324d85893887731762c08997f04059eb2ac4caf' 
  AND token = 'xXks/sYoXwGxKmJvayvnG4dlJOyAx/AaN2nge3xE3xE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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