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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b309835b2eb48dcd46d7783a0142d73c337ed00b88f428f8d4cb0ce20856e1f9' 
  AND token = '/1E/wM/mBlJ3mgt+dzuxdMuE1dXNqV25gMLNHxRTXy4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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