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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b843f8f13996a39f72a6df246ab2923c3d70ddfc37052a9562686b2cfe6372d' 
  AND token = 'grSjyCAA77FjdyzuR4Ic23qAKX3+IXqYvLJVCTDzN+E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00063

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}