SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf9c9f81a1daa820548c8a9bdb698d28a923f35742ea8aaeedad38c308d7d941' 
  AND token = 'IImftM/EJGnUVpD+nGdqM1EDSIU+WAGSxSyBxD34Hfk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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