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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a51c57cb4bfbeacd9eed9fa0d4160693a4517149c4d7265543e5dbfaabd373' 
  AND token = 'i9cJVroRmmEYkfUZD+ar88DK6eTScIhDxr8zirhs5GY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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