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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a845c520c411c951b3a5cc201f0ac24ede0b604d420e7b32b43efe3242d03c' 
  AND token = 'hyDqhdCvFj0josH1PUMawO4BG5GUhz7uNFFdRz27CaE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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