SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '375380ed7226d389fd4d77c831c2571397f7c896aaa055a1fa11be96bcdde1b4' 
  AND token = 'KDsnm5QpK841bOglLMHkFxFIgUJg1KI72njfegTQeo0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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