SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b951448f1ee3c9041325134e78967a5d9c46564024c03fca4dd310badf2e6a20' 
  AND token = '3uv9s7BX5hw7qYJPVMC21lRsHqff9MGQvpFVpu0q96U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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