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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15c6c849577aeb17ba00ae6d4a35f3d39f8f0e1d12e5c1ff757e1640ea70e96c' 
  AND token = 'NQe5eQzXdYuDavMN/kkdX42lZyiGTvjqpelRHsoZRRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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