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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f8a40ca5c6277c4cc6d0545f7d528dae5df87f9e63afd99c077aa7d3e984e740' 
  AND token = '5ZFQyAGr9nMwWt1vfywrtkAb0CKKK9re5AllpWEAj2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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