SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd188644a378989bf2f31d00c3b404d14d97360da9d5ea9e65a85bb0f182ec864' 
  AND token = '6ZMUSOxPzS2bs/rfUpLQs61+4IHrFTTPTxRTHhppvw0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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