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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b6e88de4eafdcfcbe649aa6070b10a3690b8fcb53e0e2bf26f703c8fe23fc7b' 
  AND token = 'Nr7eQrmsXsbr3p7Y8T1sPh5DcDfGLYv6lv44RqQReGQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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