SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '947823938425af5962dd7d41eb51fa08f427c1b9125b5ecc3ff6c113808b4a53' 
  AND token = 'XF20DjU5QXXFWUyQlJK1zJjF3ECXliJfwRsCUtNuDCo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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