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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '81c0b5b9399881b6d58eb381f195cca3d6c08beadafc4dfc4f892f3b7141575c' 
  AND token = 'vpcgETvaHCkK3ygqKYRg608GSeU0crLhMD+RV0fsMDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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