SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4708759a9aad38d0d02edc3be27b5715e9a4debd42da7a0db7255cbfaa5c0ea' 
  AND token = '55EkUXELmJTOmGOoeRoCeeJBiDgVhMhu/pX04B9/RBI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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