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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '536b81e42590d484c2e377efa23c15866999796510ea104d3281b76eba76b043' 
  AND token = 'E5cHfPvNkADiC7pfhymB/7cYFXB16qY90zIfvH45uus=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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