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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '476e9ee87beea0979347bd526d4ad9121504489e98ef252367afd79a070c4aff' 
  AND token = '672eSx8xZ4GujTUElxcV7XTRGopCN2zazJ2gOnG4EA8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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