SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e75b621b96fa52418d1eecdd9c3cf5690920c5862123d8efbf764aa28e40d4d0' 
  AND token = 'G+9vOoiCsVu/0WLUHgPB3kjE+oxmTpHnSS/u/0yOU0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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