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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a3f0f990e81b63f7189a768ff70ee0df63361c34d692abc243bd7f564d33b7ec' 
  AND token = 'M8kVrwV8LYd099fR9TImHV714P7/ae8dgAekT4wj81E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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