SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'bd914841a4ac4035b468c4b8ff39a7b1b76c79487d6dce7f46a00fe62bea6b6c' 
  AND token = 'i+QkjlWLK+1VcMm8Fq8bg1yorHP/C++tOwGOg/rSrJg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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