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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bcfc408a9a731f83b7408fc6a281f6e12efed8af694ee76be1d6c436296b71ad' 
  AND token = 'n/YrCyXeXS0kOpi0X+qdz3lfeNKs2TqZ1kgV4xqNpfQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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