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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a9cd3b039f644b175fa7ebeff014ce32794edc33fb53e35df1fbf62242bd84b' 
  AND token = 'e3dbMTQGiaDwflCDPymKagdK4oP0/1g+KukPVzvUnBU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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