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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '666b8d218543ef30132ecdbdb65be58944a2f3a27990f6dfee4b375bb71da23f' 
  AND token = 'aMIViPJwX/7hNOLjCdpLSuMDuWuv7asQ6n7qtpaJF1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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