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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6f1f8aaae20b0219c586cdd8cbe4683c9ac9a80b43e0602e4bf04ae8b23be57c' 
  AND token = '8zNJT+C8obIMb5x+dbXWOpD2yX0lQV1L7JwPv4Nsm1E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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