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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '54270cb74587b5fcc1c6e87e4ffa5942f4c555f0c2e51044525f5d7ad7822e95' 
  AND token = '0L8r+JKS7adiNE+vxFzxtQ2UCo/dPwKL3nRo5ubbR2A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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