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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af878e77b06463cdde3fd748ad5ad57518203eaf35c3fb355f4aacc0b9ab9bf3' 
  AND token = '+o/nD34l4hJ+LJR+NrUjRxsE2oxOWBtPMLg+OEqwMsk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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