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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a12f3df157e0ebe422c79eee792cc3824cc7962c2325fd6d8da15ab877da148d' 
  AND token = '6LrfitQwCpciMtfWc2RlS9q9fb9fhjknTT6CHisBemo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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