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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df88f0efe405e94a51b90bf74e39460053d94d0d86a6afded8f2e5004af4e4c0' 
  AND token = 'itaGU79LfGUW1L+IT2VQstVj76OjaGfVR/mWMhC54rI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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