SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b31f420e0ee1a3fbc9cd571a2ba2ae936fbe61072c04a9f4e10788b58356c599' 
  AND token = 'bAG7nfOk1Y3WqFDr1Gw34Ji+pt7Odu4VD8Bf9eOGwyI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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