SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6c045a662864dee88c823873ef73646151d35aced09699da55693ab67f5b0f5' 
  AND token = 'g0JrmDZSHcXWNvkxqyR4WU+oDIrCmmBjsdzDf4W6348=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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