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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4777dffd87107b2e481cdd2336e745b942d4020bc74c99713b16914f6a6cf450' 
  AND token = '7QN4RM9mn2c00rspTKqnxKX9K+67IJKmifWLEL760to=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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