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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21671e50c3545f9e277cc064cb12dd60ed29c91c5d8fbcc493ede0b6cdcd20f' 
  AND token = '9L9uI8fDICvmAAZdD+TbtLzNY77AldSVuLZ0FXywSJM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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