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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0100cc15702e38f75014f8c334392d43ca2fddebe172dac8ce1e522d9e508c7a' 
  AND token = '5s+1XsfgJqPlcXbgEGYZAbCKgSpZ74vhObNjNwc9JmA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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