SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52f95b60e70cf20cad84ddebfaad56949eba682a0f3b029575235f2355deef34' 
  AND token = 'GTQUixYk38Z8GyAXMCiVixEzGDWEoBM/lsLBYSn6uOE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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