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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ad6c0bd658bc7521294c7041b42d0d1fde4aa321a17452a7372e35d15704ce6' 
  AND token = 'tbMLIgBSIDnXNgYVwrVd/7nApTkEGMkaQkCgOy4IUAM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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