SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768649ce3c5b5cb274f545dd3df1a46f26dece69900d1281234c50799fefd947' 
  AND token = '3Q/iBhRdQwv0ICoGsD7iVyUjCcuHdsczRsrDKFYcZIw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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