SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fff822b6c0933788f130ddc19514b714c90db14dfdae2be095d94e82c04f58f' 
  AND token = 'YVBSYFD1i8FhZSprTJG4YXgBAss8vObyEPD4UehBQGA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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