SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a234d41da638713b88191da61605b770fd5caccc5f43a900b5ff76e5e9af0049' 
  AND token = 'TSlNBi23Iej8roSZouHMx3BwzdGbT9PRnmoT9xjgtl0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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