SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd8b21e820e9f0dd994e128b0fa41455d4a3b1a836bf6dfb547861b1cb5db4d0c' 
  AND token = 'l0SED28LY7W4FLBs5kUKwLwZf6HXfC6s0e/lFMYv/h8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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