SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3c781ee3d504a4edbd5f31510d62c847a339f1b5a0230a44a529687550619e45' 
  AND token = 'WCaPzXRcir7MWASC0NRSarEz9FZGBHF2DnPHulblt3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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