SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '842b0a483f8c1fc421ff10089e22c91ec6e4185d1ac57d717e0046a96daf38cf' 
  AND token = 'nrpsiL4PWBchtIeU4mLNyB8oNzxLvSn2x8WYEy1tEko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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