SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c23b4be63c974039936cded2ce26eeb5916308ab9572793d5008f9000328c4f4' 
  AND token = 'PWhjvzYtiywBq+gz5uHiO1XIkPKuVOwkFacQFpcVFd8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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