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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39a362b9f88634f676bc4e12802be7f7f80c06d78fd7ea133406600ef6621ec4' 
  AND token = 'UBlgRxiawzmuAnHtbGGVmOzW4e+cforkEa8rc6rag08=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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