SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a76d9965ceff93f4dfeef420808aa1e6df3a6e506053fc2cfa23db2041bd2364' 
  AND token = 'P6tAmse+cfmVZjx8ngcRAzFNZVM6pkeJEg0aL5aD2fE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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