SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '729bc66212ceee7f203c00ea54608635842498aa8b0bbbe95990b2ee1bd3a6dc' 
  AND token = 'kWkWAsIsGSC6dW4imy+Ect0mNr0znU5HeNhDD5gC2qQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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