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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878ab241bf2ecc8e7bbac2fe7832c4eb96e57480d9faa1afc9bde71aa321dc20' 
  AND token = 'UrOL8AJak+dQa6I6mdoOGsXxWkqgRc21Ra47RHODJPg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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