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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2c343c687234aba01a333013e6fb5162d7a2255b9a9800c2a2e3c3ddd393134c' 
  AND token = '4tJpl2G8Ro9YNhmUQoCWxUTHWIpmkD4GYGU7+0Cs/aQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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