SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55b8f00f251e31b29d964a97abab0b29ca20ddcd1371028f7653d02bf9ee03f5' 
  AND token = '+KJBvIur72DP1BgwtDYTpWytjbqwSoh5A+IYixOYz5o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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