SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dfb9acc43d3acbeecc8279c0e1415e8b675eae1fea2dde9e1eb6d192ed0340ab' 
  AND token = 'j0p2dRlB0qEMp2sT3tgUQqjBlrfrknN1DjSa/2qUfT8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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