SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd256c7cf4c02f9cf6f71e27ad1a8e45004933eec63749a65359204b181f040fa' 
  AND token = 'M+lCGscCjpWxZFu3oKbIvTXdgibiflWaAVXYpEh51FY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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