SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '917e2bf08b6d6b4b1e0b672c5503e122559945b822229811952e6bd4d286f5e2' 
  AND token = 'z0FGe1gALmZpIiDNM4PENcWgSXzlAEcfhUQ5WOYbEUM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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