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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71e8dda606ec0a0776bab6a589ae01d8dd3ea12e1d9ccae1bfee0b62ca6db0fa' 
  AND token = 'MSCKaMrXku2R5UzOicVhY1+1Lgih+dUCsQxHFVpOHqg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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