SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e16b1296bfb2223e14c2007a40f7a874d4700e7cc41ab027309d8345639f9337' 
  AND token = 'ajsXBE34EV5dzDk2lOPY3jkLveIMkgnsK3PDAhmpspA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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