SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6709896496fbe59b6ff1e49f75a3b831272aeeb90ed232647db1527e3909ce61' 
  AND token = '/+llqOBthpkgzdpCENJOxhU4KEyfp8wsS10SG5RhwH4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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