SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5f4b19827237f79c86235851d1937df4b168ad09a5e22c9f311804c52bf4c06' 
  AND token = 'm8POmOntntv3F8k0TQTsN8elcT3xXQWzAK5P+ArSqpA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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