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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12b8a119c4197cd7fd088552542f7dd6a83473d84548e07152c86d9b8dad17c8' 
  AND token = '4QTDslnMDhRKFC9cWwBp3lobznC3nQl0up4w6GpI42g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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