SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '843784772959445035bc5a07203061af1f387fea9664ff71fe2b7f1f7a9f3076' 
  AND token = 'v8gZ939MujCzi5uY8IyNPOhJ0mVnZhrxyicdzCsFYuI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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