SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f486ecf31a0b34f079e399c265c914b32d6787d24b430125b9b31fa46bdab5' 
  AND token = 'dXfJqVuVqN9blFvKU1tlqbBrpxd5Bg+NdeoGA1YgILA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

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