SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b278ab90d36d144bdbf07821c39a2696f03f8af86e777171e536fcfc6dfb82ed' 
  AND token = 'eKENLIEG9Sc5/A+Dh0rJm4sZDyVjChp/SJ257ro1VwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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