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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5348d2558161092381f1924149f4421af5a8abb232811ddd5cbc5a84e37a8ec4' 
  AND token = 'g10vC1xogm+5HghUTuCXNciyCfiSC7icglqhBIfNaYw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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