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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76284af7ca1aad754149a127b14d04d31b6f666339dde577a35f4b683cd13e87' 
  AND token = '/4VINiH/NUYMqV7IqbKaokNWrdxG7byVjoajNMHbftw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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