SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '835f74dd9123c33dcb2756644e3bfa9356a17243a3c1f816b597376439a239d2' 
  AND token = 'b1RC1cHfmhRBvXpFl+zcMCQhXilY+S9gROAND5V4qSI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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