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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f839ba653acf9e748476e7157ea81da2e8b45cfbb6e022ab6b942df9ee57f0' 
  AND token = 'KgssD6gCRuirdZlN7DYMUO5KqywPO49V71mFTWtaldc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}