SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50cfa65da33c4df2e639fad482d3365420caa3cb994ef5b009ff5eed49b37376' 
  AND token = 'Fp7kTmlD6soaAYzIdk5StH4fCzIAsH7ae6NlJkXzDHs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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