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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21651c6c7baa91592167233b71adc5323dbd5383d2baf6ddd89ca239a0f91a5e' 
  AND token = 'Xf3Wgd12JMIKjECbAYXZL9UvbSpCI2pBtrNzExuJ9Hc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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