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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '826e1dffdabfd18fa74aa49d3b6f8fbccee0398a0f11ee92d614b217d9615606' 
  AND token = 'xym1EerWTKEKmb+zkQ9KD3O4dKQIqOGZTGYGeGYowJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}