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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2c6cd4bf2d9d68e5782ca361fa0fe7d84cc071309da4f6cdcf6a8a3c33be79a4' 
  AND token = 'SKg2AY6y31rDuRZ5fiBo0Reuby/BEWsNXz4GFspCTUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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