SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4cfcb0def84c921004ee00359690365e6f173fa07021ddd6d72b2dca62ff7f6' 
  AND token = 'ZR96EbOnnfbUjnz720nDh3QwMmDd1MyjdbtVe6KUB3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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