SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '548039f6b30fada689a242f7e7d9c594c39e231eea15f0b352848d92b2caebea' 
  AND token = '0YvUqA9pUTKBJx6KIhIycwMYuY6CRHSCzUsPC6tlanI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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