SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '255190dceb7cc46e46f70149e833c2e23647c0cc31bcfc32cf7719ba76756c6f' 
  AND token = 'MUBSf81vUrSEfVf09irVlXvt5S1GeDcVksMbxSny8CI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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