SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4a2f943ad104056fec813fff8dee2d5f57f36a90eb131ef2103e8903d20f5f5' 
  AND token = '6e2PqNYAztB8ZmuUcYYvLlhqeEqgm7qGDHK2LBQGVPY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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