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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '51519ad9754ed060fa790f83cd6e7ff23a46badda13c3df8eabc65f6559e4a20' 
  AND token = '+0LRnD0+dkYADvYbuSddMaJGsJdSKg3HJgQ02cmqvDs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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