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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e51d64aad511c9e5f4539348337badd5c3ac306e5ebf898cdaefb2ae634d0701' 
  AND token = 'UWdEorab9GA9Z4WdUmAevYJv+DxwRxbNzTwn7zFvVao=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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