SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21a7a6731ecf0c246edb861d4e5d9bec2801bdb8f30914542ead6cc269681fe2' 
  AND token = 'hjgsA81qWdv+Lu/CpqnOKi/X6DK+JuZvwNKAAJ7IZVs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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