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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f349f836587ef0633e74ea5492e6a82b2e29efadc8ab121f3bf98c86e904194b' 
  AND token = 'pLIwSM7ULHl3comItD8sv4JCQl9+AqKNq0dTW4QCfD0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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