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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73809bf2b5b8e5b3a9f99c430e9594532b41c62ecf0aeb6097a9eaad89854349' 
  AND token = 'ZfOnzzjaJMuNhnsBGPxTR8WyWew+tecqVvTZVSOmyzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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