SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af686b5317da8f50ae59d67bb3cee4ae4e71f258ab3d6ce777f0adeff1ce991d' 
  AND token = '+bFjIcuLY9ICiWtSbp1YuC3bKXqlPbP/BRXxSYwSoHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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