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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7c61da8aa385d8907618b26c6e75d6103f0d0368c034fb95fa17e2af7ad78206' 
  AND token = 'U/rG40bxw9QClonDUFQYdDK7sKs+NCS71rqFui3WNjo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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