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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79d16b6bcdabf352e7a268c081648ca8c3fbbcd7f765697eeb2c0a0612fd87bd' 
  AND token = '8fhIrSx+j/oZwWGcETfQyImLzFGdbDbMb03FVjO5/Ks=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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