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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8c6fc4f2294521bb99cc0633d98ad91cea8bb57c715b986aa1c6a66292d52428' 
  AND token = 'VACnNrPTuDV40kXsQDnRBItMRFWgzbxb65voZ2QhCPY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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