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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '20fcda3cb1360477e732a550e40c1821225503f501ce3bd9e1018a55695c303d' 
  AND token = '80Cb81TRWTwJocKbwify49bm62utTMd6MrPxgIyd2Bs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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