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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c81dddf1490a70f0ea126978cb5c2f428c04663fa2df2566d17c3bafc6e19895' 
  AND token = 'E7phIzJ75lbO35kCkz7Rjs0Aq7rE9/sG1Ai4zRWK1aI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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