SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '816c644277906949ebd1ed968d7553c68b4f7653479059de10657a5220baca9c' 
  AND token = 'm7VOnOMQjquOII8kUaTi46ixFBXEtCk7SjDD3mzZcT0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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