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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3f846438efedbb44a2b4a0d675e3f508c8333df5be91432dd5d258d56e6f4f0' 
  AND token = 'hr4jeH7fnw6BrHR8kMzaGJOh7oMcHtLekbMhN4EUCWQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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