SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '284e20c0ccbbbe50e41cebaec76f522ab622fbaaf02ea7f25e1a879d74ddc91d' 
  AND token = 'x/K2JfMoeqqeXWfwk9nlGxLOkSfejXN/FXLpRFgOZOc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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