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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0343e8a94b18e66bc8278664f0491e49ce1e891f9fc90281f05bad2752d3ea04' 
  AND token = 'nt9YnLDj+QFYNqo+AOXgkf+VE84uOHvoGqlDincg/E4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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