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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '303f0467639bb092d5a0cba90975a190617f51a4d94be2cbd409d39613e715cd' 
  AND token = 'PHYdw1UjQpFaocqy285CWEtzhSqMKTK9Dtu1r4WcmuM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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