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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c0c74aa0ee911dbffe3fa8495137b3971ee431a5d2b0f5bb5e89136536e0fd51' 
  AND token = 'md8PARoLsZuUK9mWptdNhR6C2yI5OCLsc0jHhva1Cbo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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