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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6297e474277eafbf009a656e566b24e50c3ddd56a1172738da63da37bae94d4' 
  AND token = 'TTtubAzD81xu0c11UUu70pKuQ0hRW1A+u1Ednirxx7Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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