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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a750975c1d329d7c8d8366a1f45e14af7ca25403ce2d8ec4125fecf01abb40ac' 
  AND token = 'nJI3tCLeFaWlbghZsCYAEYPbs96zUBsBU1ia5PmagC4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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